Multichip package link

ABSTRACT

Physical layer logic is provided that is to receive data on one or more data lanes of a physical link, receive a valid signal on another of the lanes of the physical link identifying that valid data is to follow assertion of the valid signal on the one or more data lanes, and receive a stream signal on another of the lanes of the physical link identifying a type of the data on the one or more data lanes.

FIELD

This disclosure pertains to computing system, and in particular (but notexclusively) to point-to-point interconnects.

BACKGROUND

Advances in semi-conductor processing and logic design have permitted anincrease in the amount of logic that may be present on integratedcircuit devices. As a corollary, computer system configurations haveevolved from a single or multiple integrated circuits in a system tomultiple cores, multiple hardware threads, and multiple logicalprocessors present on individual integrated circuits, as well as otherinterfaces integrated within such processors. A processor or integratedcircuit typically comprises a single physical processor die, where theprocessor die may include any number of cores, hardware threads, logicalprocessors, interfaces, memory, controller hubs, etc.

As a result of the greater ability to fit more processing power insmaller packages, smaller computing devices have increased inpopularity. Smartphones, tablets, ultrathin notebooks, and other userequipment have grown exponentially. However, these smaller devices arereliant on servers both for data storage and complex processing thatexceeds the form factor. Consequently, the demand in thehigh-performance computing market (i.e. server space) has alsoincreased. For instance, in modern servers, there is typically not onlya single processor with multiple cores, but also multiple physicalprocessors (also referred to as multiple sockets) to increase thecomputing power. But as the processing power grows along with the numberof devices in a computing system, the communication between sockets andother devices becomes more critical.

In fact, interconnects have grown from more traditional multi-drop busesthat primarily handled electrical communications to full blowninterconnect architectures that facilitate fast communication.Unfortunately, as the demand for future processors to consume at evenhigher-rates corresponding demand is placed on the capabilities ofexisting interconnect architectures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a computing system including aninterconnect architecture.

FIG. 2 illustrates an embodiment of a interconnect architectureincluding a layered stack.

FIG. 3 illustrates an embodiment of a request or packet to be generatedor received within an interconnect architecture.

FIG. 4 illustrates an embodiment of a transmitter and receiver pair foran interconnect architecture.

FIG. 5 illustrates an embodiment of a multichip package.

FIG. 6 is a simplified block diagram of a multichip package link (MCPL).

FIG. 7 is a representation of example signaling on an example MCPL.

FIG. 8 is a simplified block diagram illustrating a data lane in anexample MCPL.

FIG. 9 is a simplified block diagram illustrating example crosstalkcancellation techniques in an embodiment of an MCPL.

FIG. 10 is a simplified circuit diagram illustrating example crosstalkcancellation components in an embodiment of an MCPL.

FIG. 11 is a simplified block diagram of an MCPL.

FIG. 12 is a simplified block diagram of an MCPL interfacing with upperlayer logic of multiple protocols using a logical PHY interface (LPIF).

FIG. 13 is a representation of example signaling on an example MCPL inconnection with a recovery of a link.

FIGS. 14A-14C are example bit mappings of data on lanes of an exampleMCPL.

FIG. 15 is a representation of a portion of an example link statemachine.

FIG. 16 is a representation of a flow associated with an examplecentering of a link.

FIG. 17 is a representation of an example link state machine.

FIG. 18 is a representation of signaling to enter a low power state.

FIG. 19 illustrates an embodiment of a block diagram for a computingsystem including a multicore processor.

FIG. 20 illustrates another embodiment of a block diagram for acomputing system including a multicore processor.

FIG. 21 illustrates an embodiment of a block diagram for a processor.

FIG. 22 illustrates another embodiment of a block diagram for acomputing system including a processor.

FIG. 23 illustrates an embodiment of a block for a computing systemincluding multiple processors.

FIG. 24 illustrates an example system implemented as system on chip(SoC).

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth,such as examples of specific types of processors and systemconfigurations, specific hardware structures, specific architectural andmicro architectural details, specific register configurations, specificinstruction types, specific system components, specificmeasurements/heights, specific processor pipeline stages and operationetc. in order to provide a thorough understanding of the presentinvention. It will be apparent, however, to one skilled in the art thatthese specific details need not be employed to practice the presentinvention. In other instances, well known components or methods, such asspecific and alternative processor architectures, specific logiccircuits/code for described algorithms, specific firmware code, specificinterconnect operation, specific logic configurations, specificmanufacturing techniques and materials, specific compilerimplementations, specific expression of algorithms in code, specificpower down and gating techniques/logic and other specific operationaldetails of computer system haven't been described in detail in order toavoid unnecessarily obscuring the present invention.

Although the following embodiments may be described with reference toenergy conservation and energy efficiency in specific integratedcircuits, such as in computing platforms or microprocessors, otherembodiments are applicable to other types of integrated circuits andlogic devices. Similar techniques and teachings of embodiments describedherein may be applied to other types of circuits or semiconductordevices that may also benefit from better energy efficiency and energyconservation. For example, the disclosed embodiments are not limited todesktop computer systems or Ultrabooks™. And may be also used in otherdevices, such as handheld devices, tablets, other thin notebooks,systems on a chip (SOC) devices, and embedded applications. Someexamples of handheld devices include cellular phones, Internet protocoldevices, digital cameras, personal digital assistants (PDAs), andhandheld PCs. Embedded applications typically include a microcontroller,a digital signal processor (DSP), a system on a chip, network computers(NetPC), set-top boxes, network hubs, wide area network (WAN) switches,or any other system that can perform the functions and operations taughtbelow. Moreover, the apparatus', methods, and systems described hereinare not limited to physical computing devices, but may also relate tosoftware optimizations for energy conservation and efficiency. As willbecome readily apparent in the description below, the embodiments ofmethods, apparatus', and systems described herein (whether in referenceto hardware, firmware, software, or a combination thereof) are vital toa ‘green technology’ future balanced with performance considerations.

As computing systems are advancing, the components therein are becomingmore complex. As a result, the interconnect architecture to couple andcommunicate between the components is also increasing in complexity toensure bandwidth requirements are met for optimal component operation.Furthermore, different market segments demand different aspects ofinterconnect architectures to suit the market's needs. For example,servers require higher performance, while the mobile ecosystem issometimes able to sacrifice overall performance for power savings. Yet,it's a singular purpose of most fabrics to provide highest possibleperformance with maximum power saving. Below, a number of interconnectsare discussed, which would potentially benefit from aspects of theinvention described herein.

One interconnect fabric architecture includes the Peripheral ComponentInterconnect (PCI) Express (PCIe) architecture. A primary goal of PCIeis to enable components and devices from different vendors tointer-operate in an open architecture, spanning multiple marketsegments; Clients (Desktops and Mobile), Servers (Standard andEnterprise), and Embedded and Communication devices. PCI Express is ahigh performance, general purpose I/O interconnect defined for a widevariety of future computing and communication platforms. Some PCIattributes, such as its usage model, load-store architecture, andsoftware interfaces, have been maintained through its revisions, whereasprevious parallel bus implementations have been replaced by a highlyscalable, fully serial interface. The more recent versions of PCIExpress take advantage of advances in point-to-point interconnects,Switch-based technology, and packetized protocol to deliver new levelsof performance and features. Power Management, Quality Of Service (QoS),Hot-Plug/Hot-Swap support, Data Integrity, and Error Handling are amongsome of the advanced features supported by PCI Express.

Referring to FIG. 1, an embodiment of a fabric composed ofpoint-to-point Links that interconnect a set of components isillustrated. System 100 includes processor 105 and system memory 110coupled to controller hub 115. Processor 105 includes any processingelement, such as a microprocessor, a host processor, an embeddedprocessor, a co-processor, or other processor. Processor 105 is coupledto controller hub 115 through front-side bus (FSB) 106. In oneembodiment, FSB 106 is a serial point-to-point interconnect as describedbelow. In another embodiment, link 106 includes a serial, differentialinterconnect architecture that is compliant with different interconnectstandard.

System memory 110 includes any memory device, such as random accessmemory (RAM), non-volatile (NV) memory, or other memory accessible bydevices in system 100. System memory 110 is coupled to controller hub115 through memory interface 116. Examples of a memory interface includea double-data rate (DDR) memory interface, a dual-channel DDR memoryinterface, and a dynamic RAM (DRAM) memory interface.

In one embodiment, controller hub 115 is a root hub, root complex, orroot controller in a Peripheral Component Interconnect Express (PCIe orPCIE) interconnection hierarchy. Examples of controller hub 115 includea chipset, a memory controller hub (MCH), a northbridge, an interconnectcontroller hub (ICH), a southbridge, and a root controller/hub. Oftenthe term chipset refers to two physically separate controller hubs, i.e.a memory controller hub (MCH) coupled to an interconnect controller hub(ICH). Note that current systems often include the MCH integrated withprocessor 105, while controller 115 is to communicate with I/O devices,in a similar manner as described below. In some embodiments,peer-to-peer routing is optionally supported through root complex 115.

Here, controller hub 115 is coupled to switch/bridge 120 through seriallink 119. Input/output modules 117 and 121, which may also be referredto as interfaces/ports 117 and 121, include/implement a layered protocolstack to provide communication between controller hub 115 and switch120. In one embodiment, multiple devices are capable of being coupled toswitch 120.

Switch/bridge 120 routes packets/messages from device 125 upstream, i.e.up a hierarchy towards a root complex, to controller hub 115 anddownstream, i.e. down a hierarchy away from a root controller, fromprocessor 105 or system memory 110 to device 125. Switch 120, in oneembodiment, is referred to as a logical assembly of multiple virtualPCI-to-PCI bridge devices. Device 125 includes any internal or externaldevice or component to be coupled to an electronic system, such as anI/O device, a Network Interface Controller (NIC), an add-in card, anaudio processor, a network processor, a hard-drive, a storage device, aCD/DVD ROM, a monitor, a printer, a mouse, a keyboard, a router, aportable storage device, a Firewire device, a Universal Serial Bus (USB)device, a scanner, and other input/output devices. Often in the PCIevernacular, such as device, is referred to as an endpoint. Although notspecifically shown, device 125 may include a PCIe to PCI/PCI-X bridge tosupport legacy or other version PCI devices. Endpoint devices in PCIeare often classified as legacy, PCIe, or root complex integratedendpoints.

Graphics accelerator 130 is also coupled to controller hub 115 throughserial link 132. In one embodiment, graphics accelerator 130 is coupledto an MCH, which is coupled to an ICH. Switch 120, and accordingly I/Odevice 125, is then coupled to the ICH. I/O modules 131 and 118 are alsoto implement a layered protocol stack to communicate between graphicsaccelerator 130 and controller hub 115. Similar to the MCH discussionabove, a graphics controller or the graphics accelerator 130 itself maybe integrated in processor 105.

Turning to FIG. 2 an embodiment of a layered protocol stack isillustrated. Layered protocol stack 200 includes any form of a layeredcommunication stack, such as a Quick Path Interconnect (QPI) stack, aPCie stack, a next generation high performance computing interconnectstack, or other layered stack. Although the discussion immediately belowin reference to FIGS. 1-4 are in relation to a PCIe stack, the sameconcepts may be applied to other interconnect stacks. In one embodiment,protocol stack 200 is a PCIe protocol stack including transaction layer205, link layer 210, and physical layer 220. An interface, such asinterfaces 117, 118, 121, 122, 126, and 131 in FIG. 1, may berepresented as communication protocol stack 200. Representation as acommunication protocol stack may also be referred to as a module orinterface implementing/including a protocol stack.

PCI Express uses packets to communicate information between components.Packets are formed in the Transaction Layer 205 and Data Link Layer 210to carry the information from the transmitting component to thereceiving component. As the transmitted packets flow through the otherlayers, they are extended with additional information necessary tohandle packets at those layers. At the receiving side the reverseprocess occurs and packets get transformed from their Physical Layer 220representation to the Data Link Layer 210 representation and finally(for Transaction Layer Packets) to the form that can be processed by theTransaction Layer 205 of the receiving device.

Transaction Layer

In one embodiment, transaction layer 205 is to provide an interfacebetween a device's processing core and the interconnect architecture,such as data link layer 210 and physical layer 220. In this regard, aprimary responsibility of the transaction layer 205 is the assembly anddisassembly of packets (i.e., transaction layer packets, or TLPs). Thetranslation layer 205 typically manages credit-base flow control forTLPs. PCIe implements split transactions, i.e. transactions with requestand response separated by time, allowing a link to carry other trafficwhile the target device gathers data for the response.

In addition PCIe utilizes credit-based flow control. In this scheme, adevice advertises an initial amount of credit for each of the receivebuffers in Transaction Layer 205. An external device at the opposite endof the link, such as controller hub 115 in FIG. 1, counts the number ofcredits consumed by each TLP. A transaction may be transmitted if thetransaction does not exceed a credit limit. Upon receiving a response anamount of credit is restored. An advantage of a credit scheme is thatthe latency of credit return does not affect performance, provided thatthe credit limit is not encountered.

In one embodiment, four transaction address spaces include aconfiguration address space, a memory address space, an input/outputaddress space, and a message address space. Memory space transactionsinclude one or more of read requests and write requests to transfer datato/from a memory-mapped location. In one embodiment, memory spacetransactions are capable of using two different address formats, e.g., ashort address format, such as a 32-bit address, or a long addressformat, such as 64-bit address. Configuration space transactions areused to access configuration space of the PCIe devices. Transactions tothe configuration space include read requests and write requests.Message space transactions (or, simply messages) are defined to supportin-band communication between PCIe agents.

Therefore, in one embodiment, transaction layer 205 assembles packetheader/payload 206. Format for current packet headers/payloads may befound in the PCIe specification at the PCIe specification website.

Quickly referring to FIG. 3, an embodiment of a PCIe transactiondescriptor is illustrated. In one embodiment, transaction descriptor 300is a mechanism for carrying transaction information. In this regard,transaction descriptor 300 supports identification of transactions in asystem. Other potential uses include tracking modifications of defaulttransaction ordering and association of transaction with channels.

Transaction descriptor 300 includes global identifier field 302,attributes field 304 and channel identifier field 306. In theillustrated example, global identifier field 302 is depicted comprisinglocal transaction identifier field 308 and source identifier field 310.In one embodiment, global transaction identifier 302 is unique for alloutstanding requests.

According to one implementation, local transaction identifier field 308is a field generated by a requesting agent, and it is unique for alloutstanding requests that require a completion for that requestingagent. Furthermore, in this example, source identifier 310 uniquelyidentifies the requestor agent within a PCIe hierarchy. Accordingly,together with source ID 310, local transaction identifier 308 fieldprovides global identification of a transaction within a hierarchydomain.

Attributes field 304 specifies characteristics and relationships of thetransaction. In this regard, attributes field 304 is potentially used toprovide additional information that allows modification of the defaulthandling of transactions. In one embodiment, attributes field 304includes priority field 312, reserved field 314, ordering field 316, andno-snoop field 318. Here, priority sub-field 312 may be modified by aninitiator to assign a priority to the transaction. Reserved attributefield 314 is left reserved for future, or vendor-defined usage. Possibleusage models using priority or security attributes may be implementedusing the reserved attribute field.

In this example, ordering attribute field 316 is used to supply optionalinformation conveying the type of ordering that may modify defaultordering rules. According to one example implementation, an orderingattribute of “0” denotes default ordering rules are to apply, wherein anordering attribute of “1” denotes relaxed ordering, wherein writes canpass writes in the same direction, and read completions can pass writesin the same direction. Snoop attribute field 318 is utilized todetermine if transactions are snooped. As shown, channel ID Field 306identifies a channel that a transaction is associated with.

Link Layer

Link layer 210, also referred to as data link layer 210, acts as anintermediate stage between transaction layer 205 and the physical layer220. In one embodiment, a responsibility of the data link layer 210 isproviding a reliable mechanism for exchanging Transaction Layer Packets(TLPs) between two components a link. One side of the Data Link Layer210 accepts TLPs assembled by the Transaction Layer 205, applies packetsequence identifier 211, i.e. an identification number or packet number,calculates and applies an error detection code, i.e. CRC 212, andsubmits the modified TLPs to the Physical Layer 220 for transmissionacross a physical to an external device.

Physical Layer

In one embodiment, physical layer 220 includes logical sub block 221 andelectrical sub-block 222 to physically transmit a packet to an externaldevice. Here, logical sub-block 221 is responsible for the “digital”functions of Physical Layer 221. In this regard, the logical sub-blockincludes a transmit section to prepare outgoing information fortransmission by physical sub-block 222, and a receiver section toidentify and prepare received information before passing it to the LinkLayer 210.

Physical block 222 includes a transmitter and a receiver. Thetransmitter is supplied by logical sub-block 221 with symbols, which thetransmitter serializes and transmits onto to an external device. Thereceiver is supplied with serialized symbols from an external device andtransforms the received signals into a bit-stream. The bit-stream isde-serialized and supplied to logical sub-block 221. In one embodiment,an 8b/10b transmission code is employed, where ten-bit symbols aretransmitted/received. Here, special symbols are used to frame a packetwith frames 223. In addition, in one example, the receiver also providesa symbol clock recovered from the incoming serial stream.

As stated above, although transaction layer 205, link layer 210, andphysical layer 220 are discussed in reference to a specific embodimentof a PCIe protocol stack, a layered protocol stack is not so limited. Infact, any layered protocol may be included/implemented. As an example,an port/interface that is represented as a layered protocol includes:(1) a first layer to assemble packets, i.e. a transaction layer; asecond layer to sequence packets, i.e. a link layer; and a third layerto transmit the packets, i.e. a physical layer. As a specific example, acommon standard interface (CSI) layered protocol is utilized.

Referring next to FIG. 4, an embodiment of a PCIe serial point to pointfabric is illustrated. Although an embodiment of a PCIe serialpoint-to-point link is illustrated, a serial point-to-point link is notso limited, as it includes any transmission path for transmitting serialdata. In the embodiment shown, a basic PCIe link includes two,low-voltage, differentially driven signal pairs: a transmit pair 406/411and a receive pair 412/407. Accordingly, device 405 includestransmission logic 406 to transmit data to device 410 and receivinglogic 407 to receive data from device 410. In other words, twotransmitting paths, i.e. paths 416 and 417, and two receiving paths,i.e. paths 418 and 419, are included in a PCIe link.

A transmission path refers to any path for transmitting data, such as atransmission line, a copper line, an optical line, a wirelesscommunication channel, an infrared communication link, or othercommunication path. A connection between two devices, such as device 405and device 410, is referred to as a link, such as link 415. A link maysupport one lane—each lane representing a set of differential signalpairs (one pair for transmission, one pair for reception). To scalebandwidth, a link may aggregate multiple lanes denoted by xN, where N isany supported Link width, such as 1, 2, 4, 8, 12, 16, 32, 64, or wider.

A differential pair refers to two transmission paths, such as lines 416and 417, to transmit differential signals. As an example, when line 416toggles from a low voltage level to a high voltage level, i.e. a risingedge, line 417 drives from a high logic level to a low logic level, i.e.a falling edge. Differential signals potentially demonstrate betterelectrical characteristics, such as better signal integrity, i.e.cross-coupling, voltage overshoot/undershoot, ringing, etc. This allowsfor better timing window, which enables faster transmission frequencies.

FIG. 5 is a simplified block diagram 500 illustrating an examplemulti-chip package 505 that includes two or more chips, or dies, (e.g.,510, 515) communicatively connected using an example multi-chip packagelink (MCPL) 520. While FIG. 5 illustrates an example of two (or more)dies that are interconnected using an example MCPL 520, it should beappreciated that the principles and features described herein regardingimplementations of an MCPL can be applied to any interconnect or linkconnecting a die (e.g., 510) and other components, including connectingtwo or more dies (e.g., 510, 515), connecting a die (or chip) to anothercomponent off-die, connecting a die to another device or die off-package(e.g., 505), connecting die to a BGA package, implementation of a Patchon Interposer (POINT), among potentially other examples.

Generally, a multichip package (e.g., 505) can be an electronic packagewhere multiple integrated circuits (ICs), semiconductor dies or otherdiscrete components (e.g., 510, 515) are packaged onto a unifyingsubstrate (e.g., silicon or other semiconductor substrate), facilitatingthe combined components' use as a single component (e.g., as though alarger IC). In some instances, the larger components (e.g., dies 510,515) can themselves be IC systems, such as systems on chip (SoC),multiprocessor chips, or other components that include multiplecomponents (e.g., 525-530 and 540-545) on the device, for instance, on asingle die (e.g., 510, 515). Multichip packages 505 can provideflexibility for building complex and varied systems from potentiallymultiple discrete components and systems. For instance, each of dies510, 515 may be manufactured or otherwise provided by two differententities, with the silicon substrate of the package 505 provided by yeta third entity, among many other examples. Further, dies and othercomponents within a multichip package 505 can themselves includeinterconnect or other communication fabrics (e.g., 535, 550) providingthe infrastructure for communication between components (e.g., 525-530and 540-545) within the device (e.g., 510, 515 respectively). Thevarious components and interconnects (e.g., 535, 550) may potentiallysupport or use multiple different protocols. Further, communicationbetween dies (e.g., 510, 515) can potentially include transactionsbetween the various components on the dies over multiple differentprotocols. Designing mechanisms to provide communication between chips(or dies) on a multichip package can be challenging, with traditionalsolutions employing highly specialized, expensive, and package-specificsolutions based on the specific combinations of components (and desiredtransactions) sought to be interconnected.

The examples, systems, algorithms, apparatus, logic, and featuresdescribed within this Specification can address at least some of theissues identified above, including potentially many others notexplicitly mentioned herein. For instance, in some implementations, ahigh bandwidth, low power, low latency interface can be provided toconnect a host device (e.g., a CPU) or other device to a companion chipthat sits in the same package as the host. Such a multichip package link(MCPL) can support multiple package options, multiple I/O protocols, aswell as Reliability, Availability, and Serviceability (RAS) features.Further, the physical layer (PHY) can include an electrical layer andlogic layer and can support longer channel lengths, including channellengths up to, and in some cases exceeding, approximately 45 mm. In someimplementations, an example MCPL can operate at high data rates,including data rates exceeding 8-10 Gb/s.

In one example implementation of an MCPL, a PHY electrical layer canimprove upon traditional multi-channel interconnect solutions (e.g.,multi-channel DRAM I/O), extending the data rate and channelconfiguration, for instance, by a number of features including, asexamples, regulated mid-rail termination, low power active crosstalkcancellation, circuit redundancy, per bit duty cycle correction anddeskew, line coding, and transmitter equalization, among potentiallyother examples.

In one example implementation of an MCPL, a PHY logical layer can beimplemented that can further assist (e.g., electrical layer features) inextending the data rate and channel configuration while also enablingthe interconnect to route multiple protocols across the electricallayer. Such implementations can provide and define a modular commonphysical layer that is protocol agnostic and architected to work withpotentially any existing or future interconnect protocol.

Turning to FIG. 6, a simplified block diagram 600 is shown representingat least a portion of a system including an example implementation of amultichip package link (MCPL). An MCPL can be implemented using physicalelectrical connections (e.g., wires implemented as lanes) connecting afirst device 605 (e.g., a first die including one or moresub-components) with a second device 610 (e.g., a second die includingone or more other sub-components). In the particular example shown inthe high-level representation of diagram 600, all signals (in channels615, 620) can be unidirectional and lanes can be provided for the datasignals to have both an upstream and downstream data transfer. While theblock diagram 600 of FIG. 6, refers to the first component 605 as theupstream component and the second component 610 as the downstreamcomponents, and physical lanes of the MCPL used in sending data as adownstream channel 615 and lanes used for receiving data (from component610) as an upstream channel 620, it should be appreciated that the MCPLbetween devices 605, 610 can be used by each device to both send andreceive data between the devices.

In one example implementation, an MCPL can provide a physical layer(PHY) including the electrical MCPL PHY 625 a,b (or, collectively, 625)and executable logic implementing MCPL logical PHY 630 a,b (or,collectively, 630). Electrical, or physical, PHY 625 can provide thephysical connection over which data is communicated between devices 605,610. Signal conditioning components and logic can be implemented inconnection with the physical PHY 625 in order to establish high datarate and channel configuration capabilities of the link, which in someapplications can involve tightly clustered physical connections atlengths of approximately 45 mm or more. The logical PHY 630 can includelogic for facilitating clocking, link state management (e.g., for linklayers 635 a, 635 b), and protocol multiplexing between potentiallymultiple, different protocols used for communications over the MCPL.

In one example implementation, physical PHY 625 can include, for eachchannel (e.g., 615, 620) a set of data lanes, over which in-band datacan be sent. In this particular example, 50 data lanes are provided ineach of the upstream and downstream channels 615, 620, although anyother number of lanes can be used as permitted by the layout and powerconstraints, desired applications, device constraints, etc. Each channelcan further include one or more dedicated lanes for a strobe, or clock,signal for the channel, one or more dedicated lanes for a valid signalfor the channel, one or more dedicated lanes for a stream signal, andone or more dedicated lanes for a link state machine management orsideband signal. The physical PHY can further include a sideband link640, which, in some examples, can be a bi-directional lower frequencycontrol signal link used to coordinate state transitions and otherattributes of the MCPL connecting devices 605, 610, among otherexamples.

As noted above, multiple protocols can be supported using animplementation of MCPL. Indeed, multiple, independent transaction layers650 a, 650 b can be provided at each device 605, 610. For instance, eachdevice 605, 610 may support and utilize two or more protocols, such asPCI, PCIe, QPI, Intel In-Die Interconnect (IDI), among others. IDI is acoherent protocol used on-die to communicate between cores, Last LevelCaches (LLCs), memory, graphics, and IO controllers. Other protocols canalso be supported including Ethernet protocol, Infiniband protocols, andother PCIe fabric based protocols. The combination of the Logical PHYand physical PHY can also be used as a die-to-die interconnect toconnect a SerDes PHY (PCIe, Ethernet, Infiniband or other high speedSerDes) on one Die to its upper layers that are implemented on the otherdie, among other examples.

Logical PHY 630 can support multiplexing between these multipleprotocols on an MCPL. For instance, the dedicated stream lane can beused to assert an encoded stream signal that identifies which protocolis to apply to data sent substantially concurrently on the data lanes ofthe channel. Further, logical PHY 630 can be used to negotiate thevarious types of link state transitions that the various protocols maysupport or request. In some instances, LSM_SB signals sent over thechannel's dedicated LSM_SB lane can be used, together with side bandlink 640 to communicate and negotiate link state transitions between thedevices 605, 610. Further, link training, error detection, skewdetection, de-skewing, and other functionality of traditionalinterconnects can be replaced or governed, in part using logical PHY630. For instance, valid signals sent over one or more dedicated validsignal lanes in each channel can be used to signal link activity, detectskew, link errors, and realize other features, among other examples. Inthe particular example of FIG. 6, multiple valid lanes are provided perchannel. For instance, data lanes within a channel can be bundled orclustered (physically and/or logically) and a valid lane can be providedfor each cluster. Further, multiple strobe lanes can be provided, insome cases, also to provide a dedicated strobe signal for each clusterin a plurality of data lane clusters in a channel, among other examples.

As noted above, logical PHY 630 can be used to negotiate and manage linkcontrol signals sent between devices connected by the MCPL. In someimplementations, logical PHY 630 can include link layer packet (LLP)generation logic 660 that can be used to send link layer controlmessages over the MCPL (i.e., in band). Such messages can be sent overdata lanes of the channel, with the stream lane identifying that thedata is link layer-to-link layer messaging, such as link layer controldata, among other examples. Link layer messages enabled using LLP module660 can assist in the negotiation and performance of link layer statetransitioning, power management, loopback, disable, re-centering,scrambling, among other link layer features between the link layers 635a, 635 b of devices 605, 610 respectively.

Turning to FIG. 7, a diagram 700 is shown representing example signalingusing a set of lanes (e.g., 615, 620) in a particular channel of anexample MCPL. In the example of FIG. 7, two clusters of twenty-five (25)data lanes are provided for fifty (50) total data lanes in the channel.A portion of the lanes are shown, while others (e.g., DATA[4-46] and asecond strobe signal lane (STRB)) are omitted (e.g., as redundantsignals) for convenience in illustrating the particular example. Whenthe physical layer is in an active state (e.g., not powered off or in alow power mode (e.g., an L1 state)), strobe lanes (STRB) can be providedwith a synchronous clock signal. In some implementations, data can besent on both the rising and falling edges of the strobe. Each edge (orhalf clock cycle) can demarcate a unit interval (UI). Accordingly, inthis example, a bit (e.g., 705) can be sent on each lane, allowing for abyte to be sent every 8UI. A byte time period 710 can be defined as 8UI,or the time for sending a byte on a single one of the data lanes (e.g.,DATA[0-49]).

In some implementations, a valid signal, sent on one or more dedicatedvalid signal channels (e.g., VALID0, VALID1), can serve as a leadingindicator for the receiving device to identify, when asserted (high), tothe receiving device, or sink, that data is being sent from the sendingdevice, or source, on data lanes (e.g., DATA[0-49]) during the followingtime period, such as a byte time period 710. Alternatively, when thevalid signal is low, the source indicates to the sink that the sink willnot be sending data on the data lanes during the following time period.Accordingly, when the sink logical PHY detects that the valid signal isnot asserted (e.g., on lanes VALID0 and VALID1), the sink can disregardany data that is detected on the data lanes (e.g., DATA[0-49]) duringthe following time period. For instance, cross talk noise or other bitsmay appear on one or more of the data lanes when the source, in fact, isnot sending any data. By virtue of a low, or non-asserted, valid signalduring the previous time period (e.g., the previous byte time period),the sink can determine that the data lanes are to be disregarded duringthe following time period.

Data sent on each of the lanes of the MCPL can be strictly aligned tothe strobe signal. A time period can be defined based on the strobe,such as a byte time period, and each of these periods can correspond toa defined window in which signals are to be sent on the data lanes(e.g., DATA[0-49]), the valid lanes (e.g., VALID1, VALID2), and streamlane (e.g., STREAM). Accordingly, alignment of these signals can enableidentification that a valid signal in a previous time period windowapplies to data in the following time period window, and that a streamsignal applies to data in the same time period window. The stream signalcan be an encoded signal (e.g., 1 byte of data for a byte time periodwindow), that is encoded to identify the protocol that applies to databeing sent during the same time period window.

To illustrate, in the particular example of FIG. 7, a byte time periodwindow is defined. A valid is asserted at a time period window n ( 715),before any data is injected on data lanes DATA[0-49]. At the followingtime period window n+1 (720) data is sent on at least some of the datalanes. In this case, data is sent on all fifty data lanes during n+1 (720). Because a valid was asserted for the duration of the precedingtime period window n ( 715), the sink device can validate the datareceived on data lanes DATA[0-49] during time period window n+1 (720).Additionally, the leading nature of the valid signal during time periodwindow n (715) allows the receiving device to prepare for the incomingdata. Continuing with the example of FIG. 7, the valid signal remainsasserted (on VALID1 and VALID2) during the duration of time periodwindow n+1 (720), causing the sink device to expect the data sent overdata lanes DATA[0-49] during time period window n+2 (725). If the validsignal were to remain asserted during time period window n+2 (725), thesink device could further expect to receive (and process) additionaldata sent during an immediately subsequent time period window n+3 (730).In the example of FIG. 7, however, the valid signal is de-assertedduring the duration of time period window n+2 (725), indicating to thesink device that no data will be sent during time period window n+3(730) and that any bits detected on data lanes DATA[0-49] should bedisregarded during time period window n+3 (730).

As noted above, multiple valid lanes and strobe lanes can be maintainedper channel. This can assist, among other advantages, with maintainingcircuit simplicity and synchronization amid the clusters of relativelylengthy physical lanes connecting the two devices. In someimplementations, a set of data lanes can be divided into clusters ofdata lanes. For instance, in the example of FIG. 7, data lanesDATA[0-49] can be divided into two twenty-five lane clusters and eachcluster can have a dedicated valid and strobe lane. For instance, validlane VALID1 can be associated with data lanes DATA[0-24] and valid laneVALID2 can be associated with data lanes DATA[25-49]. The signals oneach “copy” of the valid and strobe lanes for each cluster can beidentical.

As introduced above, data on stream lane STREAM can be used to indicateto the receiving logical PHY what protocol is to apply to correspondingdata being sent on data lanes data lanes DATA[0-49]. In the example ofFIG. 7, a stream signal is sent on STREAM during the same time periodwindow as data on data lanes DATA[0-49] to indicate the protocol of thedata on the data lanes. In alternative implementations, the streamsignal can be sent during a preceding time period window, such as withcorresponding valid signals, among other potential modifications.However, continuing with the example of FIG. 7, a stream signal 735 issent during time period window n+1 (720) that is encoded to indicate theprotocol (e.g., PCIe, PCI, IDI, QPI, etc.) that is to apply to the bitssent over data lanes DATA[0-49] during time period window n+1 (720).Similarly, another stream signal 740 can be sent during the subsequenttime period window n+2 (725) to indicate the protocol that applies tothe bits sent over data lanes DATA[0-49] during time period window n+2(725), and so on. In some cases, such as the example of FIG. 7 (whereboth stream signals 735, 740 have the same encoding, binary FF), data insequential time period windows (e.g., n+1 (720) and n+2 (725)) canbelong to the same protocol. However, in other cases, data in sequentialtime period windows (e.g., n+1 (720) and n+2 (725)) can be fromdifferent transactions to which different protocols are to apply, andstream signals (e.g., 735, 740) can be encoded accordingly to identifythe different protocols applying to the sequential bytes of data on thedata lanes (e.g., DATA[0-49]), among other examples.

In some implementations, a low power or idle state can be defined forthe MCPL. For instance, when neither device on the MCPL is sending data,the physical layer (electrical and logical) of MCPL can go to an idle orlow power state. For instance, in the example of FIG. 7, at time periodwindow n−2 (745), the MCPL is in a quiet or idle state and the strobe isdisabled to save power. The MCPL can transition out of low-power or idlemode, awaking the strobe at time period window time period window n−1(e.g., 705). The strobe can complete a transmission preamble (e.g., toassist in waking and synchronizing each of the lanes of the channel, aswell as the sink device), beginning the strobe signal prior to any othersignaling on the other non-strobe lanes. Following this time periodwindow n−1 (705), the valid signal can be asserted at time period windown (715) to notify the sink that data is forthcoming in the followingtime period window n+1 (720), as discussed above.

The MCPL may re-enter a low power or idle state (e.g., an L1 state)following the detection of idle conditions on the valid lanes, datalanes, and/or other lanes of the MCPL channel. For instance, nosignaling may be detected beginning at time period window n+3 (730) andgoing forward. Logic on either the source or sink device can initiatetransition back into a low power state leading again (e.g., time periodwindow n+5 (755)) to the strobe going idle in a power savings mode,among other examples and principles (including those discussed laterherein).

Electrical characteristics of the physical PHY can include one or moreof single-ended signaling, half-rate forwarded clocking, matching ofinterconnect channel as well as on-chip transport delay of transmitter(source) and receiver (sink), optimized electrostatic discharge (ESD)protection, pad capacitance, among other features. Further, an MCPL canbe implemented to achieve higher data rate (e.g., approaching 16 Gb/s)and energy efficiency characteristics than traditional package I/Osolutions.

FIG. 8 illustrates a portion of a simplified block diagram 800representing a portion of an example MCPL. The diagram 800 of FIG. 8includes a representation of an example lane 805 (e.g., a data lane,valid lane, or stream lane) and clock generation logic 810. As shown inthe example of FIG. 8, in some implementations, clock generation logic810 can be implemented as a clock tree to distribute the generated clocksignal to each block implementing each lane of the example MCPL, such asdata lane 805. Further, a clock recovery circuit 815 can be provided. Insome implementations, rather than providing a separate clock recoverycircuit for each lane in which the clock signal is distributed, as iscustomary in at least some traditional interconnect I/O architectures, asingle clock recovery circuit can be provided for a cluster of aplurality of lanes. Indeed, as applied to the example configurations inFIGS. 6 and 7, a separate strobe lane and accompanying clock recoverycircuit can be provided for each cluster of twenty-five data lanes.

Continuing with the example of FIG. 8, in some implementations, at leastthe data lanes, stream lanes, and valid lanes can be terminated,mid-rail, to a regulated voltage greater than zero (ground). In someimplementations, a mid-rail voltage can be regulated to Vcc/2. In someimplementations, a single voltage regulator 825 can be provided percluster of lanes. For instance, when applied to the examples of FIGS. 6and 7, a first voltage regulator can be provided for a first cluster oftwenty-five data lanes and a second voltage regulator can be providedfor the remaining cluster of twenty-five data lanes, among otherpotential examples. In some instances, an example voltage regulator 825can be implemented as a linear regulator, a switched capacitor circuit,among other examples. In some implementations, the linear regulator canbe provided with analog feedback loop or digital feedback loop, amongother examples.

In some implementations, crosstalk cancellation circuitry can also beprovided for an example MCPL. In some instances, the compact nature ofthe long MCPL wires can introduce crosstalk interference between lanes.Crosstalk cancellation logic can be implemented to address these andother issues. For instance, in one example illustrated in FIGS. 9-10,crosstalk can be reduced significantly with an example low power activecircuit, such as illustrated in diagrams 900 and 1000. For instance, inthe example of FIG. 9, a weighted high-pass filtered “aggressor” signalcan be added to the “victim” signal (i.e., the signal sufferingcrosstalk interference from the aggressor). Each signal can beconsidered a victim of crosstalk from each other signal in the link, andcan, itself, be the aggressor to the other signal insofar it is thesource of crosstalk interference. Such a signal can be generated andreduce crosstalk on the victim lane by more than 50%, owing to thederivative nature of crosstalk on the link. The low pass filteredaggressor signal, in the example of FIG. 9, can be generated through ahigh-pass RC filter (e.g., implemented through C and R1) that producesthe filtered signal to be added using a summing circuit 905 (e.g., RXsense-amp).

Implementations similar to that described in the example of FIG. 9 canbe particularly convenient solutions for an application such as MCLP, asimplementation of the circuit can be realized with relatively lowoverhead, as illustrated in the diagram of FIG. 10 illustrating anexample transistor-level schematic of the circuit shown and described inthe example of FIG. 9. It should be appreciated that the representationsin FIGS. 9 and 10 are simplified representations, and an actualimplementation would include multiple copies of the circuits illustratedin FIGS. 9 and 10 to accommodate the network of crosstalk interferenceamong and between the lanes of a link. As an example, in a three lanelink (e.g., Lanes 0-2) circuitry similar to that described in theexamples of FIGS. 9 and 10 could be provided from Lane 0 to Lane 1, fromLane 0 to Lane 2, from Lane 1 to Lane 0, from Lane 1 to Lane 2, fromLane 2 to Lane 0, from Lane 2 to Lane 1, etc. based on the geometry andthe layout of the lanes, among other examples

Additional features can be implemented at the physical PHY level of anexample MCPL. For instance, receiver offset can introduce significanterror and limit I/O voltage margin in some instances. Circuit redundancycan be used to improve receiver sensitivity. In some implementations,circuit redundancy can be optimized to address the standard deviationoffset of data samplers used in the MCPL. For instance, an example datasampler can be provided that is designed to a three (3) standarddeviation offset specification. In the examples of FIGS. 6 and 7, forinstance, were two (2) data samplers to be used for each receiver (e.g.,for each lane), one hundred (100) samplers would be used for a fifty(50) lane MCPL. In this example, the probability that one of thereceiver (RX) lanes fails the three standard deviation offsetspecification is 24%. A chip reference voltage generator can be providedto set the offset upper-bound and move to the next data sampler on thereceiver if another one of the other data samplers is found to beexceeding the bound. However, were four (4) data samplers to be used perreceiver (i.e., instead of two in this example), the receiver will onlyfail if three out of four samplers fail. For a fifty-lane MCPL, as inthe examples of FIGS. 6 and 7, adding this additional circuit redundancycan dramatically reduce the failure rate from 24% to less than 0.01%.

In still other examples, at very high data rates, per bit duty cyclecorrection (DCC) and deskew can be used to augment baseline per clusterDCC and deskew to improve link margin. Instead of correction for allcases, as in traditional solutions, in some implementations a low powerdigital implementation can be utilized that senses and corrects theoutliers where the I/O lane would fail. For instance, a global tuning ofthe lanes can be performed to identify problem lanes within the cluster.These problem lanes can then be targeted for per-lane tuning to achievethe high data rates supported by the MCPL.

Additional features can also be optionally implemented in some examplesof a MCPL to enhance the performance characteristics of the physicallink. For instance, line coding can be provided. While mid-railterminations, such as described above, can allow for DC data businversion (DBI) to be omitted, AC DBI can still be used to reduce thedynamic power. More complicated coding can also be used to eliminate theworst case difference of 1's and 0's to reduce, for instance, the driverequirement of mid-rail regulator, as well as limit I/O switching noise,among other example benefits. Further, transmitter equalization can alsobe optionally implemented. For instance, at very high data rates,insertion loss can be a significant for an in-package channel. A two-tapweight transmitter equalization (e.g., performed during an initialpower-up sequence) can, in some cases, be sufficient to mitigate some ofthese issues, among others.

Turning to FIG. 11, a simplified block diagram 1100 is shownillustrating an example logical PHY of an example MCPL. A physical PHY1105 can connect to a die that includes logical PHY 1110 and additionallogic supporting a link layer of the MCPL. The die, in this example, canfurther include logic to support multiple different protocols on theMCPL. For instance, in the example of FIG. 11, PCIe logic 1115 can beprovided as well as IDI logic 1120, such that the dies can communicateusing either PCIe or IDI over the same MCPL connecting the two dies,among potentially many other examples, including examples where morethan two protocols or protocols other than PCIe and IDI are supportedover the MCPL. Various protocols supported between the dies can offervarying levels of service and features.

Logical PHY 1110 can include link state machine management logic 1125for negotiating link state transitions in connection with requests ofupper layer logic of the die (e.g., received over PCIe or IDI). LogicalPHY 1110 can further include link testing and debug logic (e.g., 1130)ion some implementations. As noted above, an example MCPL can supportcontrol signals that are sent between dies over the MCPL to facilitateprotocol agnostic, high performance, and power efficiency features(among other example features) of the MCPL. For instance, logical PHY1110 can support the generation and sending, as well as the receivingand processing of valid signals, stream signals, and LSM sidebandsignals in connection with the sending and receiving of data overdedicated data lanes, such as described in examples above.

In some implementations, multiplexing (e.g., 1135) and demultiplexing(e.g., 1140) logic can be included in, or be otherwise accessible to,logical PHY 1110. For instance, multiplexing logic (e.g., 1135) can beused to identify data (e.g., embodied as packets, messages, etc.) thatis to be sent out onto the MCPL. The multiplexing logic 1135 canidentify the protocol governing the data and generate a stream signalthat is encoded to identify the protocol. For instance, in one exampleimplementation, the stream signal can be encoded as a byte of twohexadecimal symbols (e.g., IDI: FFh; PCIe: F0h; LLP: AAh; sideband: 55h;etc.), and can be sent during the same window (e.g., a byte time periodwindow) of the data governed by the identified protocol. Similarly,demultiplexing logic 1140 can be employed to interpret incoming streamsignals to decode the stream signal and identify the protocol that is toapply to data concurrently received with the stream signal on the datalanes. The demultiplexing logic 1140 can then apply (or ensure)protocol-specific link layer handling and cause the data to be handledby the corresponding protocol logic (e.g., PCIe logic 1115 or IDI logic1120).

Logical PHY 1110 can further include link layer packet logic 1150 thatcan be used to handle various link control functions, including powermanagement tasks, loopback, disable, re-centering, scrambling, etc. LLPlogic 1150 can facilitate link layer-to-link layer messages over MCLP,among other functions. Data corresponding to the LLP signaling can bealso be identified by a stream signal sent on a dedicated stream signallane that is encoded to identify that the data lanes LLP data.Multiplexing and demultiplexing logic (e.g., 1135, 1140) can also beused to generate and interpret the stream signals corresponding to LLPtraffic, as well as cause such traffic to be handled by the appropriatedie logic (e.g., LLP logic 1150). Likewise, as some implementations ofan MCLP can include a dedicated sideband (e.g., sideband 1155 andsupporting logic), such as an asynchronous and/or lower frequencysideband channel, among other examples.

Logical PHY logic 1110 can further include link state machine managementlogic that can generate and receive (and use) link state managementmessaging over a dedicated LSM sideband lane. For instance, an LSMsideband lane can be used to perform handshaking to advance linktraining state, exit out of power management states (e.g., an L1 state),among other potential examples. The LSM sideband signal can be anasynchronous signal, in that it is not aligned with the data, valid, andstream signals of the link, but instead corresponds to signaling statetransitions and align the link state machine between the two die orchips connected by the link, among other examples. Providing a dedicatedLSM sideband lane can, in some examples, allow for traditional squelchand received detect circuits of an analog front end (AFE) to beeliminated, among other example benefits.

Turning to FIG. 12, a simplified block diagram 1200 is shownillustrating another representation of logic used to implement an MCPL.For instance, logical PHY 1110 is provided with a defined logical PHYinterface (LPIF) 1205 through which any one of a plurality of differentprotocols (e.g., PCIe, IDI, QPI, etc.) 1210, 1215, 1220, 1225 andsignaling modes (e.g., sideband) can interface with the physical layerof an example MCPL. In some implementations, multiplexing andarbitration logic 1230 can also be provided as a layer separate from thelogical PHY 1110. In one example, the LPIF 1205 can be provided as theinterface on either side of this MuxArb layer 1230. The logical PHY 1110can interface with the physical PHY (e.g., the analog front end (AFE)1105 of the MCPL PHY) through another interface.

The LPIF can abstract the PHY (logical and electrical/analog) from theupper layers (e.g., 1210, 1215, 1220, 1225) such that a completelydifferent PHY can be implemented under LPIF transparent to the upperlayers. This can assist in promoting modularity and re-use in design, asthe upper layers can stay intact when the underlying signalingtechnology PHY is updated, among other examples. Further, the LPIF candefine a number of signals enabling multiplexing/demultiplexing, LSMmanagement, error detection and handling, and other functionality of thelogical PHY. For instance, Table 1 summarizes at least a portion ofsignals that can be defined for an example LPIF:

TABLE 1 Signal Name Description Rst Reset Lclk Link Clock-8UI of PHYclock Pl_trdy Physical Layer is ready to accept data, data is acceptedby Physical layer when Pl_trdy and Lp_valid are both asserted.Pl_data[N-1:0][7:0] Physical Layer-to-Link Layer data, where N equalsthe number of lanes. Pl_valid Physical Layer-to-Link Layer signalindicating data valid Pl_Stream[7:0] Physical Layer-to-Link Layer signalindicating the stream ID received with received data Pl_error Physicallayer detected an error (e.g., framing or training) Pl_AlignReq PhysicalLayer request to Link Layer to align packets at LPIF width boundaryPl_in_L0 Indicates that link state machine (LSM) is in L0 Pl_in_retrainIndicates that LSM is in Retrain/Recovery Pl_rejectL1 Indicates that thePHY layer has rejected entry into L1. Pl_in_L12 Indicates that LSM is inL1 or L2. Pl_LSM (3:0) Current LSM state information Lp_data[N-1:0][7:0]Link Layer-to-Physical Layer Data, where N equals number of lanes.Lp_Stream[7:0] Link Layer-to-Physical Layer signal indicating the streamID to use with data Lp_AlignAck Link Layer to Physical layer indicatesthat the packets are aligned LPIF width boundary Lp_valid LinkLayer-to-Physical Layer signal indicating data valid Lp_enterL1 LinkLayer Request to Physical Layer to enter L1 Lp_enterL2 Link LayerRequest to Physical Layer to enter L2 Lp_Retrain Link Layer Request toPhysical Layer to Retrain the PHY Lp_exitL12 Link Layer Request toPhysical Layer to exit L1, L2 Lp_Disable Link Layer Request to PhysicalLayer to disable PHY

As noted in Table 1, in some implementations, an alignment mechanism canbe provided through an AlignReq/AlignAck handshake. For example, whenthe physical layer enters recovery, some protocols may lose packetframing. Alignment of the packets can be corrected, for instance, toguarantee correct framing identification by the link layer.Additionally, as shown in FIG. 13, the physical layer can assert aStallReq signal when it enters recovery, such that the link layerasserts a Stall signal when a new aligned packet is ready to betransferred. The physical layer logic can sample both Stall and Valid todetermine if the packet is aligned. For instance, the physical layer cancontinue to drive trdy to drain the link layer packets until Stall andValid are sampled asserted, among other potential implementations,including other alternative implementations using Valid to assist inpacket alignment.

Various fault tolerances can be defined for signals on the MCPL. Forinstance, fault tolerances can be defined for valid, stream, LSMsideband, low frequency side band, link layer packets, and other typesof signals. Fault tolerances for packets, messages, and other data sentover the dedicated data lanes of the MCPL can be based on the particularprotocol governing the data. In some implementations, error detectionand handling mechanisms can be provided, such as cyclic redundancy check(CRC), retry buffers, among other potential examples. As examples, forPCIe packets sent over the MCPL, 32-bit CRC can be utilized for PCIetransaction layer packets (TLPs) (with guaranteed delivery (e.g.,through a replay mechanism)) and 16-bit CRC can be utilized for PCIelink layer packets (which may be architected to be lossy (e.g., wherereplay is not applied)). Further, for PCIe framing tokens, a particularhamming distance (e.g., hamming distance of four (4)) can be defined forthe token identifier; parity and 4-bit CRC can also be utilized, amongother examples. For IDI packets, on the other hand, 16-bit CRC can beutilized.

In some implementations, fault tolerances can be defined for link layerpackets (LLPs) that include requiring a valid signal to transition fromlow to high (i.e., 0-to-1) (e.g., to assist in assuring bit and symbollock). Further, in one example, a particular number of consecutive,identical LLPs can be defined to be sent and responses can be expectedto each request, with the requestor retrying after a response timeout,among other defined characteristics that can be used as the basis ofdetermining faults in LLP data on the MCPL. In further examples, faulttolerance can be provided for a valid signal, for instance, throughextending the valid signal across an entire time period window, orsymbol (e.g., by keeping the valid signal high for eight UIs).Additionally, errors or faults in stream signals can be prevented bymaintaining a hamming distance for encodings values of the streamsignal, among other examples.

Implementations of a logical PHY can include error detection, errorreporting, and error handling logic. In some implementations, a logicalPHY of an example MCPL can include logic to detect PHY layer de-framingerrors (e.g., on the valid and stream lanes), sideband errors (e.g.,relating to LSM state transitions), errors in LLPs (e.g., that arecritical to LSM state transitions), among other examples. Some errordetection/resolution can be delegated to upper layer logic, such as PCIelogic adapted to detect PCIe-specific errors, among other examples.

In the case of de-framing errors, in some implementations, one or moremechanisms can be provided through error handling logic. De-framingerrors can be handled based on the protocol involved. For instance, insome implementations, link layers can be informed of the error totrigger a retry. De-framing can also cause a realignment of the logicalPHY de-framing. Further, re-centering of the logical PHY can beperformed and symbol/window lock can be reacquired, among othertechniques. Centering, in some examples, can include the PHY moving thereceiver clock phase to the optimal point to detect the incoming data.“Optimal,” in this context, can refer to where it has the most marginfor noise and clock jitter. Re-centering can include simplifiedcentering functions, for instance, performed when the PHY wakes up froma low power state, among other examples.

Other types of errors can involve other error handling techniques. Forinstance, errors detected in a sideband can be caught through a time-outmechanism of a corresponding state (e.g., of an LSM). The error can belogged and the link state machine can then be transitioned to Reset. TheLSM can remain in Reset until a restart command is received fromsoftware. In another example, LLP errors, such as a link control packeterror, can be handled with a time-out mechanism that can re-start theLLP sequence if an acknowledgement to the LLP sequence is not received.

FIGS. 14A-14C illustrate representations of example bit mappings on datalanes of an example MCPL for various types of data. For instance, anexample MCPL can include fifty data lanes. FIG. 14A illustrates a firstbit mapping of example 16 byte slots in a first protocol, such as IDI,that can be sent over the data lanes within an 8UI symbol, or window.For instance, within the defined 8UI window, three 16 byte slots,including a header slot, can be sent. Two bytes of data remain, in thisexample, and these remaining two bytes can be utilized CRC bits (e.g.,in lanes DATA[48] and DATA[49]).

In another example, FIG. 14B illustrates a second example bit mappingfor PCIe packet data sent over the fifty data lanes of an example MCPL.In the example of FIG. 14B, 16 bytes packets (e.g., transaction layer(TLP) or data link layer (DLLP) PCIe packets) can be sent over the MCPL.In an 8UI window, three packets can be sent, with the remaining twobytes of bandwidth left unused within the window. Framing tokens can beincluded in these symbols and used to locate the start and end of eachpacket. In one example of PCIe, the framing utilized in the example ofFIG. 14B can be the same as those token implemented for PCIe at 8GT/s.

In yet another example, illustrated in FIG. 14C, an example bit mappingof link-to-link packets (e.g., LLP packets) sent over an example MCPL isshown. LLPs can be 4 bytes each and each LLP (e.g., LLP0, LLP1, LLP2,etc.) can be sent four consecutive times, in accordance with faulttolerance and error detection within an example implementation. Forinstance, failure to receive four consecutive identical LLPs canindicate an error. Additionally, as with other data types, failure toreceive a VALID in a proceeding time window, or symbol, can alsoindicate an error. In some instances, LLPs can have fixed slots.Additionally, in this example, unused, or “spare,” bits in the byte timeperiod, can result in logical 0s being transmitted over two of the fiftylanes (e.g., DATA[48-49]), among other examples.

Turning to FIG. 15, a simplified link state machine transition diagram1400 is shown together with sideband handshaking utilized between thestate transitions. For instance, a Reset.Idle state (e.g., where phaselock loop (PLL) lock calibration is performed) can transition, through asideband handshake, to a Reset.Cal state (e.g., where the link isfurther calibrated). Reset.Cal can transition, through a sidebandhandshake, to a Reset.ClockDCC state (e.g., where duty cycle correction(DCC) and delay-locked looping (DLL) lock can be performed). Anadditional handshake can be performed to transition from Reset.ClockDCCto a Reset.Quiet state (e.g., to deassert the Valid signal). To assistin alignment of signaling on the lanes of the MCPL, the lanes can becentered through a Center.Pattern state.

In some implementations, as shown in the example of FIG. 16, during theCenter.Pattern state, the transmitter can generate training patterns orother data. The receiver can condition its receiver circuitry to receivesuch training patterns, for instance, by setting the phase interpolatorposition and vref position and setting the comparator. The receiver cancontinuously compare the patterns received with expected patterns andstore the result in a register. After one set of patterns are complete,the receiver can increment the phase interpolator setting keeping thevref the same. The test pattern generation and comparison process cancontinue and new compare results can be stored in the register with theprocedure repeatedly stepping through all phase interpolator values andthrough all values of vref. The Center.Quiet state can be entered whenthe pattern generation and comparison process is all complete. Followingthe centering of the lanes through the Center.Pattern and Center Quietlink states, a sideband handshake (e.g., using an LSM sideband signalover the dedicated LSM sideband lane of the link) can be facilitated totransition to a Link Init state to initialize the MCPL and enablesending of data on the MCPL.

Returning momentarily to the discussion of FIG. 15, as noted above,sideband handshakes can be used to facilitate link state machinetransitions between dies or chips in a multi-chip package. For instance,signals on the LSM sideband lanes of an MCPL can be used to synchronizethe state machine transitions across the die. For example, when theconditions to exit a state (e.g., Reset.Idle) are met, the side that metthose conditions can assert, on its outbound LSM_SB lane, an LSMsideband signal and wait for the other remote die to reach the samecondition and assert an LSM sideband signal on its LSM_SB lane. Whenboth LSM_SB signals are asserted the link state machine of eachrespective die can transition to the next state (e.g., a Reset.Calstate). A minimum overlap time can be defined during which both LSM_SBsignals should be kept asserted prior to transitioning state. Further, aminimum quiesce time can be defined after LSM_SB is de-asserted to allowfor accurate turn-around detection. In some implementations, every linkstate machine transition can be conditioned on and facilitated by suchLSM_SB handshakes.

FIG. 17 is a more detailed link state machine diagram 1700, illustratingat least some of the additional link states and link state transitionsthat can be included in an example MCPL. In some implementations, anexample link state machine can include, among the other states and statetransitions illustrated in FIG. 17, a “Directed Loopback” transition canbe provided to place the lanes of an MCPL into a digital loopback. Forinstance, the receiver lanes of an MCPL can be looped back to thetransmitter lanes after the clock recovery circuits. An “LB_Recenter”state can also be provided in some instances, which can be used to alignthe data symbols. Additionally, as shown in FIG. 15, MCPL can supportmultiple link states, including an active L0 state and low power states,such as an L1 idle state, and L2 sleep state, among potentially otherexamples.

FIG. 18 is a simplified block diagram 1800 illustrating an example flowin a transition between an active state (e.g., L0) and a low-power, oridle, state (e.g., L1). In this particular example, a first device 1805and a second device 1810 are communicatively coupled using an MCPL.While in the active state, data is transmitted over the lanes of theMCPL (e.g., DATA, VALID, STREAM, etc.). Link layer packets (LLPs) can becommunicated over the lanes (e.g., data lanes, with the stream signalindicating that the data is LLP data), to assist in facilitating linkstate transitions. For instance, LLPs can be sent between the first andsecond devices 1805, 1810 to negotiate entry from L0 into L1. Forinstance, upper layer protocols supported by the MCPL can communicatethat entry into L1 (or another state) is desired and the upper layerprotocols can cause LLPs to be sent over the MCPL to facilitate a linklayer handshake to cause the physical layer to enter L1. For instance,FIG. 18 shows at least a portion of LLPs sent including an “Enter L1”request LLP sent from the second (upstream) device 1810 to the first(downstream) device 1805. In some implementations, and upper levelprotocols, the downstream port does not initiate the entry into L1. Thereceiving first device 1805 can send a “Change to L1” request LLP inresponse, which the second device 1810 can acknowledge through a “Changeto L1” acknowledgement (ACK) LLP, among other examples. Upon detectingcompletion of the handshake, the logical PHY can cause a sideband signalto be asserted on a dedicated sideband link to acknowledge that the ACKwas received and that the device (e.g., 1805) is ready for and expectingentry into L1. For instance, the first device 1805 can assert a sidebandsignal 1815 sent to the second device 1810 to confirm receipt of thefinal ACK in the link layer handshake. Additionally, the second device1810 can also assert a sideband signal in response to sideband signal1815 to notify the first device 1805 of the first device's sideband ACK1805. With the link layer control and sideband handshakes completed, theMCPL PHY can be transitioned into the L1 state causing all lanes of theMCPL to be put into idle power savings mode, including respective MCPLstrobes of the 1820, 1825 of the devices 1805, 1810. The L1 can beexited upon upper level layer logic of one of the first and seconddevices 1805, 1810 requesting re-entry into L0, for instance, inresponse to detecting data to be sent to the other device over the MCPL.

As noted above, in some implementations, an MCPL can facilitatecommunication between two devices supporting potentially multipledifferent protocols, and the MCPL can facilitate communicationsaccording to potentially any one of the multiple protocols over thelanes of the MCPL. Facilitating multiple protocols, however, cancomplicate entry and reentry into at least some link states. Forinstance, while some traditional interconnects have a single upper layerprotocol assuming the role of master in state transitions, animplementation of MCPL with multiple different protocols effectivelyinvolves multiple masters. As an example, as shown in FIG. 18, each ofPCIe and IDI can be supported between two devices 1805, 1810 over animplementation of an MCPL. For instance, placing the physical layer intoan idle or low power state may be conditioned on permission first beingobtained from each of the supported protocols (e.g., both PCIe and IDI).

In some instances, entry into L1 (or another state) may be requested byonly one of the multiple, supported protocols supported for animplementation of an MCPL. While there may be a likelihood that theother protocols will likewise request entry into the same state (e.g.,based on identifying similar conditions (e.g., little or no traffic) onthe MCPL), the logical PHY can wait until permission or instructions arereceived from each upper layer protocol before actually facilitating thestate transition. The logical PHY can track which upper layer protocolshave requested the state change (e.g., performed a correspondinghandshake) and trigger the state transition upon identifying that eachof the protocols have requested the particular state change, such as atransition from L0 to L1 or another transition that would affect orinterfere with other protocols' communications. In some implementations,protocols can be blind as to their at least partial dependence on otherprotocols in the system. Further, in some instances, a protocol mayexpect a response (e.g., from the PHY) to a request to enter aparticular state, such as a confirmation or rejection of the requestedstate transition. Accordingly, in such instances, while waiting forpermission from other supported protocols for entry into an idle linkstate, the logical PHY can generate synthetic responses to a request toenter the idle state to “trick” the requesting upper layer protocol intobelieving that a particular state has been entered (when, in reality,the lanes are still active, at least until the other protocols alsorequest entry into the idle state). Among other potential advantages,this can simplify coordinating entry into the low power state betweenmultiple protocols, among other examples.

Note that the apparatus', methods', and systems described above may beimplemented in any electronic device or system as aforementioned. Asspecific illustrations, the figures below provide exemplary systems forutilizing the invention as described herein. As the systems below aredescribed in more detail, a number of different interconnects aredisclosed, described, and revisited from the discussion above. And as isreadily apparent, the advances described above may be applied to any ofthose interconnects, fabrics, or architectures.

Referring to FIG. 19, an embodiment of a block diagram for a computingsystem including a multicore processor is depicted. Processor 1900includes any processor or processing device, such as a microprocessor,an embedded processor, a digital signal processor (DSP), a networkprocessor, a handheld processor, an application processor, aco-processor, a system on a chip (SOC), or other device to execute code.Processor 1900, in one embodiment, includes at least two cores—core 1901and 1902, which may include asymmetric cores or symmetric cores (theillustrated embodiment). However, processor 1900 may include any numberof processing elements that may be symmetric or asymmetric.

In one embodiment, a processing element refers to hardware or logic tosupport a software thread. Examples of hardware processing elementsinclude: a thread unit, a thread slot, a thread, a process unit, acontext, a context unit, a logical processor, a hardware thread, a core,and/or any other element, which is capable of holding a state for aprocessor, such as an execution state or architectural state. In otherwords, a processing element, in one embodiment, refers to any hardwarecapable of being independently associated with code, such as a softwarethread, operating system, application, or other code. A physicalprocessor (or processor socket) typically refers to an integratedcircuit, which potentially includes any number of other processingelements, such as cores or hardware threads.

A core often refers to logic located on an integrated circuit capable ofmaintaining an independent architectural state, wherein eachindependently maintained architectural state is associated with at leastsome dedicated execution resources. In contrast to cores, a hardwarethread typically refers to any logic located on an integrated circuitcapable of maintaining an independent architectural state, wherein theindependently maintained architectural states share access to executionresources. As can be seen, when certain resources are shared and othersare dedicated to an architectural state, the line between thenomenclature of a hardware thread and core overlaps. Yet often, a coreand a hardware thread are viewed by an operating system as individuallogical processors, where the operating system is able to individuallyschedule operations on each logical processor.

Physical processor 1900, as illustrated in FIG. 19, includes twocores—core 1901 and 1902. Here, core 1901 and 1902 are consideredsymmetric cores, i.e. cores with the same configurations, functionalunits, and/or logic. In another embodiment, core 1901 includes anout-of-order processor core, while core 1902 includes an in-orderprocessor core. However, cores 1901 and 1902 may be individuallyselected from any type of core, such as a native core, a softwaremanaged core, a core adapted to execute a native Instruction SetArchitecture (ISA), a core adapted to execute a translated InstructionSet Architecture (ISA), a co-designed core, or other known core. In aheterogeneous core environment (i.e. asymmetric cores), some form oftranslation, such a binary translation, may be utilized to schedule orexecute code on one or both cores. Yet to further the discussion, thefunctional units illustrated in core 1901 are described in furtherdetail below, as the units in core 1902 operate in a similar manner inthe depicted embodiment.

As depicted, core 1901 includes two hardware threads 1901 a and 1901 b,which may also be referred to as hardware thread slots 1901 a and 1901b. Therefore, software entities, such as an operating system, in oneembodiment potentially view processor 1900 as four separate processors,i.e., four logical processors or processing elements capable ofexecuting four software threads concurrently. As alluded to above, afirst thread is associated with architecture state registers 1901 a, asecond thread is associated with architecture state registers 1901 b, athird thread may be associated with architecture state registers 1902 a,and a fourth thread may be associated with architecture state registers1902 b. Here, each of the architecture state registers (1901 a, 1901 b,1902 a, and 1902 b) may be referred to as processing elements, threadslots, or thread units, as described above. As illustrated, architecturestate registers 1901 a are replicated in architecture state registers1901 b, so individual architecture states/contexts are capable of beingstored for logical processor 1901 a and logical processor 1901 b. Incore 1901, other smaller resources, such as instruction pointers andrenaming logic in allocator and renamer block 1930 may also bereplicated for threads 1901 a and 1901 b. Some resources, such asre-order buffers in reorder/retirement unit 1935, ILTB 1920, load/storebuffers, and queues may be shared through partitioning. Other resources,such as general purpose internal registers, page-table base register(s),low-level data-cache and data-TLB 1915, execution unit(s) 1940, andportions of out-of-order unit 1935 are potentially fully shared.

Processor 1900 often includes other resources, which may be fullyshared, shared through partitioning, or dedicated by/to processingelements. In FIG. 19, an embodiment of a purely exemplary processor withillustrative logical units/resources of a processor is illustrated. Notethat a processor may include, or omit, any of these functional units, aswell as include any other known functional units, logic, or firmware notdepicted. As illustrated, core 1901 includes a simplified,representative out-of-order (OOO) processor core. But an in-orderprocessor may be utilized in different embodiments. The OOO coreincludes a branch target buffer 1920 to predict branches to beexecuted/taken and an instruction-translation buffer (I-TLB) 1920 tostore address translation entries for instructions.

Core 1901 further includes decode module 1925 coupled to fetch unit 1920to decode fetched elements. Fetch logic, in one embodiment, includesindividual sequencers associated with thread slots 1901 a, 1901 b,respectively. Usually core 1901 is associated with a first ISA, whichdefines/specifies instructions executable on processor 1900. Oftenmachine code instructions that are part of the first ISA include aportion of the instruction (referred to as an opcode), whichreferences/specifies an instruction or operation to be performed. Decodelogic 1925 includes circuitry that recognizes these instructions fromtheir opcodes and passes the decoded instructions on in the pipeline forprocessing as defined by the first ISA. For example, as discussed inmore detail below decoders 1925, in one embodiment, include logicdesigned or adapted to recognize specific instructions, such astransactional instruction. As a result of the recognition by decoders1925, the architecture or core 1901 takes specific, predefined actionsto perform tasks associated with the appropriate instruction. It isimportant to note that any of the tasks, blocks, operations, and methodsdescribed herein may be performed in response to a single or multipleinstructions; some of which may be new or old instructions. Notedecoders 1926, in one embodiment, recognize the same ISA (or a subsetthereof). Alternatively, in a heterogeneous core environment, decoders1926 recognize a second ISA (either a subset of the first ISA or adistinct ISA).

In one example, allocator and renamer block 1930 includes an allocatorto reserve resources, such as register files to store instructionprocessing results. However, threads 1901 a and 1901 b are potentiallycapable of out-of-order execution, where allocator and renamer block1930 also reserves other resources, such as reorder buffers to trackinstruction results. Unit 1930 may also include a register renamer torename program/instruction reference registers to other registersinternal to processor 1900. Reorder/retirement unit 1935 includescomponents, such as the reorder buffers mentioned above, load buffers,and store buffers, to support out-of-order execution and later in-orderretirement of instructions executed out-of-order.

Scheduler and execution unit(s) block 1940, in one embodiment, includesa scheduler unit to schedule instructions/operation on execution units.For example, a floating point instruction is scheduled on a port of anexecution unit that has an available floating point execution unit.Register files associated with the execution units are also included tostore information instruction processing results. Exemplary executionunits include a floating point execution unit, an integer executionunit, a jump execution unit, a load execution unit, a store executionunit, and other known execution units.

Lower level data cache and data translation buffer (D-TLB) 1950 arecoupled to execution unit(s) 1940. The data cache is to store recentlyused/operated on elements, such as data operands, which are potentiallyheld in memory coherency states. The D-TLB is to store recentvirtual/linear to physical address translations. As a specific example,a processor may include a page table structure to break physical memoryinto a plurality of virtual pages.

Here, cores 1901 and 1902 share access to higher-level or further-outcache, such as a second level cache associated with on-chip interface1910. Note that higher-level or further-out refers to cache levelsincreasing or getting further way from the execution unit(s). In oneembodiment, higher-level cache is a last-level data cache—last cache inthe memory hierarchy on processor 1900—such as a second or third leveldata cache. However, higher level cache is not so limited, as it may beassociated with or include an instruction cache. A trace cache—a type ofinstruction cache—instead may be coupled after decoder 1925 to storerecently decoded traces. Here, an instruction potentially refers to amacro-instruction (i.e. a general instruction recognized by thedecoders), which may decode into a number of micro-instructions(micro-operations).

In the depicted configuration, processor 1900 also includes on-chipinterface module 1910. Historically, a memory controller, which isdescribed in more detail below, has been included in a computing systemexternal to processor 1900. In this scenario, on-chip interface 1910 isto communicate with devices external to processor 1900, such as systemmemory 1975, a chipset (often including a memory controller hub toconnect to memory 1975 and an I/O controller hub to connect peripheraldevices), a memory controller hub, a northbridge, or other integratedcircuit. And in this scenario, bus 1905 may include any knowninterconnect, such as multi-drop bus, a point-to-point interconnect, aserial interconnect, a parallel bus, a coherent (e.g. cache coherent)bus, a layered protocol architecture, a differential bus, and a GTL bus.

Memory 1975 may be dedicated to processor 1900 or shared with otherdevices in a system. Common examples of types of memory 1975 includeDRAM, SRAM, non-volatile memory (NV memory), and other known storagedevices. Note that device 1980 may include a graphic accelerator,processor or card coupled to a memory controller hub, data storagecoupled to an I/O controller hub, a wireless transceiver, a flashdevice, an audio controller, a network controller, or other knowndevice.

Recently however, as more logic and devices are being integrated on asingle die, such as SOC, each of these devices may be incorporated onprocessor 1900. For example in one embodiment, a memory controller hubis on the same package and/or die with processor 1900. Here, a portionof the core (an on-core portion) 1910 includes one or more controller(s)for interfacing with other devices such as memory 1975 or a graphicsdevice 1980. The configuration including an interconnect and controllersfor interfacing with such devices is often referred to as an on-core (orun-core configuration). As an example, on-chip interface 1910 includes aring interconnect for on-chip communication and a high-speed serialpoint-to-point link 1905 for off-chip communication. Yet, in the SOCenvironment, even more devices, such as the network interface,co-processors, memory 1975, graphics processor 1980, and any other knowncomputer devices/interface may be integrated on a single die orintegrated circuit to provide small form factor with high functionalityand low power consumption.

In one embodiment, processor 1900 is capable of executing a compiler,optimization, and/or translator code 1977 to compile, translate, and/oroptimize application code 1976 to support the apparatus and methodsdescribed herein or to interface therewith. A compiler often includes aprogram or set of programs to translate source text/code into targettext/code. Usually, compilation of program/application code with acompiler is done in multiple phases and passes to transform hi-levelprogramming language code into low-level machine or assembly languagecode. Yet, single pass compilers may still be utilized for simplecompilation. A compiler may utilize any known compilation techniques andperform any known compiler operations, such as lexical analysis,preprocessing, parsing, semantic analysis, code generation, codetransformation, and code optimization.

Larger compilers often include multiple phases, but most often thesephases are included within two general phases: (1) a front-end, i.e.generally where syntactic processing, semantic processing, and sometransformation/optimization may take place, and (2) a back-end, i.e.generally where analysis, transformations, optimizations, and codegeneration takes place. Some compilers refer to a middle, whichillustrates the blurring of delineation between a front-end and back endof a compiler. As a result, reference to insertion, association,generation, or other operation of a compiler may take place in any ofthe aforementioned phases or passes, as well as any other known phasesor passes of a compiler. As an illustrative example, a compilerpotentially inserts operations, calls, functions, etc. in one or morephases of compilation, such as insertion of calls/operations in afront-end phase of compilation and then transformation of thecalls/operations into lower-level code during a transformation phase.Note that during dynamic compilation, compiler code or dynamicoptimization code may insert such operations/calls, as well as optimizethe code for execution during runtime. As a specific illustrativeexample, binary code (already compiled code) may be dynamicallyoptimized during runtime. Here, the program code may include the dynamicoptimization code, the binary code, or a combination thereof.

Similar to a compiler, a translator, such as a binary translator,translates code either statically or dynamically to optimize and/ortranslate code. Therefore, reference to execution of code, applicationcode, program code, or other software environment may refer to: (1)execution of a compiler program(s), optimization code optimizer, ortranslator either dynamically or statically, to compile program code, tomaintain software structures, to perform other operations, to optimizecode, or to translate code; (2) execution of main program code includingoperations/calls, such as application code that has beenoptimized/compiled; (3) execution of other program code, such aslibraries, associated with the main program code to maintain softwarestructures, to perform other software related operations, or to optimizecode; or (4) a combination thereof.

Referring now to FIG. 20, shown is a block diagram of an embodiment of amulticore processor. As shown in the embodiment of FIG. 20, processor2000 includes multiple domains. Specifically, a core domain 2030includes a plurality of cores 2030A-2030N, a graphics domain 2060includes one or more graphics engines having a media engine 2065, and asystem agent domain 2010.

In various embodiments, system agent domain 2010 handles power controlevents and power management, such that individual units of domains 2030and 2060 (e.g. cores and/or graphics engines) are independentlycontrollable to dynamically operate at an appropriate power mode/level(e.g. active, turbo, sleep, hibernate, deep sleep, or other AdvancedConfiguration Power Interface like state) in light of the activity (orinactivity) occurring in the given unit. Each of domains 2030 and 2060may operate at different voltage and/or power, and furthermore theindividual units within the domains each potentially operate at anindependent frequency and voltage. Note that while only shown with threedomains, understand the scope of the present invention is not limited inthis regard and additional domains may be present in other embodiments.

As shown, each core 2030 further includes low level caches in additionto various execution units and additional processing elements. Here, thevarious cores are coupled to each other and to a shared cache memorythat is formed of a plurality of units or slices of a last level cache(LLC) 2040A-2040N; these LLCs often include storage and cache controllerfunctionality and are shared amongst the cores, as well as potentiallyamong the graphics engine too.

As seen, a ring interconnect 2050 couples the cores together, andprovides interconnection between the core domain 2030, graphics domain2060 and system agent circuitry 2010, via a plurality of ring stops2052A-2052N, each at a coupling between a core and LLC slice. As seen inFIG. 20, interconnect 2050 is used to carry various information,including address information, data information, acknowledgementinformation, and snoop/invalid information. Although a ring interconnectis illustrated, any known on-die interconnect or fabric may be utilized.As an illustrative example, some of the fabrics discussed above (e.g.another on-die interconnect, On-chip System Fabric (OSF), an AdvancedMicrocontroller Bus Architecture (AMBA) interconnect, amulti-dimensional mesh fabric, or other known interconnect architecture)may be utilized in a similar fashion.

As further depicted, system agent domain 2010 includes display engine2012 which is to provide control of and an interface to an associateddisplay. System agent domain 2010 may include other units, such as: anintegrated memory controller 2020 that provides for an interface to asystem memory (e.g., a DRAM implemented with multiple DIMMs; coherencelogic 2022 to perform memory coherence operations. Multiple interfacesmay be present to enable interconnection between the processor and othercircuitry. For example, in one embodiment at least one direct mediainterface (DMI) 2016 interface is provided as well as one or more PCIe™interfaces 2014. The display engine and these interfaces typicallycouple to memory via a PCIe™ bridge 2018. Still further, to provide forcommunications between other agents, such as additional processors orother circuitry, one or more other interfaces may be provided.

Referring now to FIG. 21, shown is a block diagram of a representativecore; specifically, logical blocks of a back-end of a core, such as core2030 from FIG. 20. In general, the structure shown in FIG. 21 includesan out-of-order processor that has a front end unit 2170 used to fetchincoming instructions, perform various processing (e.g. caching,decoding, branch predicting, etc.) and passing instructions/operationsalong to an out-of-order (OOO) engine 2180. OOO engine 2180 performsfurther processing on decoded instructions.

Specifically in the embodiment of FIG. 21, out-of-order engine 2180includes an allocate unit 2182 to receive decoded instructions, whichmay be in the form of one or more micro-instructions or uops, from frontend unit 2170, and allocate them to appropriate resources such asregisters and so forth. Next, the instructions are provided to areservation station 2184, which reserves resources and schedules themfor execution on one of a plurality of execution units 2186A-2186N.Various types of execution units may be present, including, for example,arithmetic logic units (ALUs), load and store units, vector processingunits (VPUs), floating point execution units, among others. Results fromthese different execution units are provided to a reorder buffer (ROB)2188, which take unordered results and return them to correct programorder.

Still referring to FIG. 21, note that both front end unit 2170 andout-of-order engine 2180 are coupled to different levels of a memoryhierarchy. Specifically shown is an instruction level cache 2172, thatin turn couples to a mid-level cache 2176, that in turn couples to alast level cache 2195. In one embodiment, last level cache 2195 isimplemented in an on-chip (sometimes referred to as uncore) unit 2190.As an example, unit 2190 is similar to system agent 2010 of FIG. 20. Asdiscussed above, uncore 2190 communicates with system memory 2199,which, in the illustrated embodiment, is implemented via ED RAM. Notealso that the various execution units 2186 within out-of-order engine2180 are in communication with a first level cache 2174 that also is incommunication with mid-level cache 2176. Note also that additional cores2130N-2-2130N can couple to LLC 2195. Although shown at this high levelin the embodiment of FIG. 21, understand that various alterations andadditional components may be present.

Turning to FIG. 22, a block diagram of an exemplary computer systemformed with a processor that includes execution units to execute aninstruction, where one or more of the interconnects implement one ormore features in accordance with one embodiment of the present inventionis illustrated. System 2200 includes a component, such as a processor2202 to employ execution units including logic to perform algorithms forprocess data, in accordance with the present invention, such as in theembodiment described herein. System 2200 is representative of processingsystems based on the PENTIUM III™, PENTIUM 4™, Xeon™, Itanium, XScale™and/or StrongARM™ microprocessors, although other systems (including PCshaving other microprocessors, engineering workstations, set-top boxesand the like) may also be used. In one embodiment, sample system 2200executes a version of the WINDOWSTM operating system available fromMicrosoft Corporation of Redmond, Wash., although other operatingsystems (UNIX and Linux for example), embedded software, and/orgraphical user interfaces, may also be used. Thus, embodiments of thepresent invention are not limited to any specific combination ofhardware circuitry and software.

Embodiments are not limited to computer systems. Alternative embodimentsof the present invention can be used in other devices such as handhelddevices and embedded applications. Some examples of handheld devicesinclude cellular phones, Internet Protocol devices, digital cameras,personal digital assistants (PDAs), and handheld PCs. Embeddedapplications can include a micro controller, a digital signal processor(DSP), system on a chip, network computers (NetPC), set-top boxes,network hubs, wide area network (WAN) switches, or any other system thatcan perform one or more instructions in accordance with at least oneembodiment.

In this illustrated embodiment, processor 2202 includes one or moreexecution units 2208 to implement an algorithm that is to perform atleast one instruction. One embodiment may be described in the context ofa single processor desktop or server system, but alternative embodimentsmay be included in a multiprocessor system. System 2200 is an example ofa ‘hub’ system architecture. The computer system 2200 includes aprocessor 2202 to process data signals. The processor 2202, as oneillustrative example, includes a complex instruction set computer (CISC)microprocessor, a reduced instruction set computing (RISC)microprocessor, a very long instruction word (VLIW) microprocessor, aprocessor implementing a combination of instruction sets, or any otherprocessor device, such as a digital signal processor, for example. Theprocessor 2202 is coupled to a processor bus 2210 that transmits datasignals between the processor 2202 and other components in the system2200. The elements of system 2200 (e.g. graphics accelerator 2212,memory controller hub 2216, memory 2220, I/O controller hub 2224,wireless transceiver 2226, Flash BIOS 2228, Network controller 2234,Audio controller 2236, Serial expansion port 2238, I/O controller 2240,etc.) perform their conventional functions that are well known to thosefamiliar with the art.

In one embodiment, the processor 2202 includes a Level 1 (L1) internalcache memory 2204. Depending on the architecture, the processor 2202 mayhave a single internal cache or multiple levels of internal caches.Other embodiments include a combination of both internal and externalcaches depending on the particular implementation and needs. Registerfile 2206 is to store different types of data in various registersincluding integer registers, floating point registers, vector registers,banked registers, shadow registers, checkpoint registers, statusregisters, and instruction pointer register.

Execution unit 2208, including logic to perform integer and floatingpoint operations, also resides in the processor 2202. The processor2202, in one embodiment, includes a microcode (ucode) ROM to storemicrocode, which when executed, is to perform algorithms for certainmacroinstructions or handle complex scenarios. Here, microcode ispotentially updateable to handle logic bugs/fixes for processor 2202.For one embodiment, execution unit 2208 includes logic to handle apacked instruction set 2209. By including the packed instruction set2209 in the instruction set of a general-purpose processor 2202, alongwith associated circuitry to execute the instructions, the operationsused by many multimedia applications may be performed using packed datain a general-purpose processor 2202. Thus, many multimedia applicationsare accelerated and executed more efficiently by using the full width ofa processor's data bus for performing operations on packed data. Thispotentially eliminates the need to transfer smaller units of data acrossthe processor's data bus to perform one or more operations, one dataelement at a time.

Alternate embodiments of an execution unit 2208 may also be used inmicro controllers, embedded processors, graphics devices, DSPs, andother types of logic circuits. System 2200 includes a memory 2220.Memory 2220 includes a dynamic random access memory (DRAM) device, astatic random access memory (SRAM) device, flash memory device, or othermemory device. Memory 2220 stores instructions and/or data representedby data signals that are to be executed by the processor 2202.

Note that any of the aforementioned features or aspects of the inventionmay be utilized on one or more interconnect illustrated in FIG. 22. Forexample, an on-die interconnect (ODI), which is not shown, for couplinginternal units of processor 2202 implements one or more aspects of theinvention described above. Or the invention is associated with aprocessor bus 2210 (e.g. other known high performance computinginterconnect), a high bandwidth memory path 2218 to memory 2220, apoint-to-point link to graphics accelerator 2212 (e.g. a PeripheralComponent Interconnect express (PCIe) compliant fabric), a controllerhub interconnect 2222, an I/O or other interconnect (e.g. USB, PCI,PCIe) for coupling the other illustrated components. Some examples ofsuch components include the audio controller 2236, firmware hub (flashBIOS) 2228, wireless transceiver 2226, data storage 2224, legacy I/Ocontroller 2210 containing user input and keyboard interfaces 2242, aserial expansion port 2238 such as Universal Serial Bus (USB), and anetwork controller 2234. The data storage device 2224 can comprise ahard disk drive, a floppy disk drive, a CD-ROM device, a flash memorydevice, or other mass storage device.

Referring now to FIG. 23, shown is a block diagram of a second system2300 in accordance with an embodiment of the present invention. As shownin FIG. 23, multiprocessor system 2300 is a point-to-point interconnectsystem, and includes a first processor 2370 and a second processor 2380coupled via a point-to-point interconnect 2350. Each of processors 2370and 2380 may be some version of a processor. In one embodiment, 2352 and2354 are part of a serial, point-to-point coherent interconnect fabric,such as a high-performance architecture. As a result, the invention maybe implemented within the QPI architecture.

While shown with only two processors 2370, 2380, it is to be understoodthat the scope of the present invention is not so limited. In otherembodiments, one or more additional processors may be present in a givenprocessor.

Processors 2370 and 2380 are shown including integrated memorycontroller units 2372 and 2382, respectively. Processor 2370 alsoincludes as part of its bus controller units point-to-point (P-P)interfaces 2376 and 2378; similarly, second processor 2380 includes P-Pinterfaces 2386 and 2388. Processors 2370, 2380 may exchange informationvia a point-to-point (P-P) interface 2350 using P-P interface circuits2378, 2388. As shown in FIG. 23, IMCs 2372 and 2382 couple theprocessors to respective memories, namely a memory 2332 and a memory2334, which may be portions of main memory locally attached to therespective processors.

Processors 2370, 2380 each exchange information with a chipset 2390 viaindividual P-P interfaces 2352, 2354 using point to point interfacecircuits 2376, 2394, 2386, 2398. Chipset 2390 also exchanges informationwith a high-performance graphics circuit 2338 via an interface circuit2392 along a high-performance graphics interconnect 2339.

A shared cache (not shown) may be included in either processor oroutside of both processors; yet connected with the processors via P-Pinterconnect, such that either or both processors' local cacheinformation may be stored in the shared cache if a processor is placedinto a low power mode.

Chipset 2390 may be coupled to a first bus 2316 via an interface 2396.In one embodiment, first bus 2316 may be a Peripheral ComponentInterconnect (PCI) bus, or a bus such as a PCI Express bus or anotherthird generation I/O interconnect bus, although the scope of the presentinvention is not so limited.

As shown in FIG. 23, various I/O devices 2314 are coupled to first bus2316, along with a bus bridge 2318 which couples first bus 2316 to asecond bus 2320. In one embodiment, second bus 2320 includes a low pincount (LPC) bus. Various devices are coupled to second bus 2320including, for example, a keyboard and/or mouse 2322, communicationdevices 2327 and a storage unit 2328 such as a disk drive or other massstorage device which often includes instructions/code and data 2330, inone embodiment. Further, an audio I/O 2324 is shown coupled to secondbus 2320. Note that other architectures are possible, where the includedcomponents and interconnect architectures vary. For example, instead ofthe point-to-point architecture of FIG. 23, a system may implement amulti-drop bus or other such architecture.

Turning next to FIG. 24, an embodiment of a system on-chip (SOC) designin accordance with the inventions is depicted. As a specificillustrative example, SOC 2400 is included in user equipment (UE). Inone embodiment, UE refers to any device to be used by an end-user tocommunicate, such as a hand-held phone, smartphone, tablet, ultra-thinnotebook, notebook with broadband adapter, or any other similarcommunication device. Often a UE connects to a base station or node,which potentially corresponds in nature to a mobile station (MS) in aGSM network.

Here, SOC 2400 includes 2 cores—2406 and 2407. Similar to the discussionabove, cores 2406 and 2407 may conform to an Instruction SetArchitecture, such as an Intel® Architecture Core™-based processor, anAdvanced Micro Devices, Inc. (AMD) processor, a MIPS-based processor, anARM-based processor design, or a customer thereof, as well as theirlicensees or adopters. Cores 2406 and 2407 are coupled to cache control2408 that is associated with bus interface unit 2409 and L2 cache 2411to communicate with other parts of system 2400. Interconnect 2410includes an on-chip interconnect, such as an IOSF, AMBA, or otherinterconnect discussed above, which potentially implements one or moreaspects of described herein.

Interface 2410 provides communication channels to the other components,such as a Subscriber Identity Module (SIM) 2430 to interface with a SIMcard, a boot rom 2435 to hold boot code for execution by cores 2406 and2407 to initialize and boot SOC 2400, a SDRAM controller 2440 tointerface with external memory (e.g. DRAM 2460), a flash controller 2445to interface with non-volatile memory (e.g. Flash 2465), a peripheralcontrol 2450 (e.g. Serial Peripheral Interface) to interface withperipherals, video codecs 2420 and Video interface 2425 to display andreceive input (e.g. touch enabled input), GPU 2415 to perform graphicsrelated computations, etc. Any of these interfaces may incorporateaspects of the invention described herein.

In addition, the system illustrates peripherals for communication, suchas a Bluetooth module 2470, 3G modem 2475, GPS 2485, and WiFi 2485. Noteas stated above, a UE includes a radio for communication. As a result,these peripheral communication modules are not all required. However, ina UE some form a radio for external communication is to be included.

While the present invention has been described with respect to a limitednumber of embodiments, those skilled in the art will appreciate numerousmodifications and variations therefrom. It is intended that the appendedclaims cover all such modifications and variations as fall within thetrue spirit and scope of this present invention.

A design may go through various stages, from creation to simulation tofabrication. Data representing a design may represent the design in anumber of manners. First, as is useful in simulations, the hardware maybe represented using a hardware description language or anotherfunctional description language. Additionally, a circuit level modelwith logic and/or transistor gates may be produced at some stages of thedesign process. Furthermore, most designs, at some stage, reach a levelof data representing the physical placement of various devices in thehardware model. In the case where conventional semiconductor fabricationtechniques are used, the data representing the hardware model may be thedata specifying the presence or absence of various features on differentmask layers for masks used to produce the integrated circuit. In anyrepresentation of the design, the data may be stored in any form of amachine readable medium. A memory or a magnetic or optical storage suchas a disc may be the machine readable medium to store informationtransmitted via optical or electrical wave modulated or otherwisegenerated to transmit such information. When an electrical carrier waveindicating or carrying the code or design is transmitted, to the extentthat copying, buffering, or re-transmission of the electrical signal isperformed, a new copy is made. Thus, a communication provider or anetwork provider may store on a tangible, machine-readable medium, atleast temporarily, an article, such as information encoded into acarrier wave, embodying techniques of embodiments of the presentinvention.

A module as used herein refers to any combination of hardware, software,and/or firmware. As an example, a module includes hardware, such as amicro-controller, associated with a non-transitory medium to store codeadapted to be executed by the micro-controller. Therefore, reference toa module, in one embodiment, refers to the hardware, which isspecifically configured to recognize and/or execute the code to be heldon a non-transitory medium. Furthermore, in another embodiment, use of amodule refers to the non-transitory medium including the code, which isspecifically adapted to be executed by the microcontroller to performpredetermined operations. And as can be inferred, in yet anotherembodiment, the term module (in this example) may refer to thecombination of the microcontroller and the non-transitory medium. Oftenmodule boundaries that are illustrated as separate commonly vary andpotentially overlap. For example, a first and a second module may sharehardware, software, firmware, or a combination thereof, whilepotentially retaining some independent hardware, software, or firmware.In one embodiment, use of the term logic includes hardware, such astransistors, registers, or other hardware, such as programmable logicdevices.

Use of the phrase ‘configured to,’ in one embodiment, refers toarranging, putting together, manufacturing, offering to sell, importingand/or designing an apparatus, hardware, logic, or element to perform adesignated or determined task. In this example, an apparatus or elementthereof that is not operating is still ‘configured to’ perform adesignated task if it is designed, coupled, and/or interconnected toperform said designated task. As a purely illustrative example, a logicgate may provide a 0 or a 1 during operation. But a logic gate‘configured to’ provide an enable signal to a clock does not includeevery potential logic gate that may provide a 1 or 0. Instead, the logicgate is one coupled in some manner that during operation the 1 or 0output is to enable the clock. Note once again that use of the term‘configured to’ does not require operation, but instead focus on thelatent state of an apparatus, hardware, and/or element, where in thelatent state the apparatus, hardware, and/or element is designed toperform a particular task when the apparatus, hardware, and/or elementis operating.

Furthermore, use of the phrases ‘to,’ capable of/to,' and or ‘operableto,’ in one embodiment, refers to some apparatus, logic, hardware,and/or element designed in such a way to enable use of the apparatus,logic, hardware, and/or element in a specified manner. Note as abovethat use of to, capable to, or operable to, in one embodiment, refers tothe latent state of an apparatus, logic, hardware, and/or element, wherethe apparatus, logic, hardware, and/or element is not operating but isdesigned in such a manner to enable use of an apparatus in a specifiedmanner.

A value, as used herein, includes any known representation of a number,a state, a logical state, or a binary logical state. Often, the use oflogic levels, logic values, or logical values is also referred to as 1'sand 0's, which simply represents binary logic states. For example, a 1refers to a high logic level and 0 refers to a low logic level. In oneembodiment, a storage cell, such as a transistor or flash cell, may becapable of holding a single logical value or multiple logical values.However, other representations of values in computer systems have beenused. For example the decimal number ten may also be represented as abinary value of 1010 and a hexadecimal letter A. Therefore, a valueincludes any representation of information capable of being held in acomputer system.

Moreover, states may be represented by values or portions of values. Asan example, a first value, such as a logical one, may represent adefault or initial state, while a second value, such as a logical zero,may represent a non-default state. In addition, the terms reset and set,in one embodiment, refer to a default and an updated value or state,respectively. For example, a default value potentially includes a highlogical value, i.e. reset, while an updated value potentially includes alow logical value, i.e. set. Note that any combination of values may beutilized to represent any number of states.

The embodiments of methods, hardware, software, firmware or code setforth above may be implemented via instructions or code stored on amachine-accessible, machine readable, computer accessible, or computerreadable medium which are executable by a processing element. Anon-transitory machine-accessible/readable medium includes any mechanismthat provides (i.e., stores and/or transmits) information in a formreadable by a machine, such as a computer or electronic system. Forexample, a non-transitory machine-accessible medium includesrandom-access memory (RAM), such as static RAM (SRAM) or dynamic RAM(DRAM); ROM; magnetic or optical storage medium; flash memory devices;electrical storage devices; optical storage devices; acoustical storagedevices; other form of storage devices for holding information receivedfrom transitory (propagated) signals (e.g., carrier waves, infraredsignals, digital signals); etc., which are to be distinguished from thenon-transitory mediums that may receive information there from.

Instructions used to program logic to perform embodiments of theinvention may be stored within a memory in the system, such as DRAM,cache, flash memory, or other storage. Furthermore, the instructions canbe distributed via a network or by way of other computer readable media.Thus a machine-readable medium may include any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputer), but is not limited to, floppy diskettes, optical disks,Compact Disc, Read-Only Memory (CD-ROMs), and magneto-optical disks,Read-Only Memory (ROMs), Random Access Memory (RAM), ErasableProgrammable Read-Only Memory (EPROM), Electrically ErasableProgrammable Read-Only Memory (EEPROM), magnetic or optical cards, flashmemory, or a tangible, machine-readable storage used in the transmissionof information over the Internet via electrical, optical, acoustical orother forms of propagated signals (e.g., carrier waves, infraredsignals, digital signals, etc.). Accordingly, the computer-readablemedium includes any type of tangible machine-readable medium suitablefor storing or transmitting electronic instructions or information in aform readable by a machine (e.g., a computer).

The following examples pertain to embodiments in accordance with thisSpecification. One or more embodiments may provide an apparatus, asystem, a machine readable storage, a machine readable medium, hardware-and/or software-based logic, and a method to receive data on one or moredata lanes of a physical link, receive a valid signal on another of thelanes of the physical link identifying that valid data is to followassertion of the valid signal on the one or more data lanes, and receivea stream signal on another of the lanes of the physical link identifyinga type of the data on the one or more data lanes.

In at least one example, physical layer logic is further to send a linkstate machine management signal over another of the lanes of thephysical link.

In at least one example, the physical layer logic is further to send asideband signal over a sideband link.

In at least one example, the type comprises a protocol associated withthe data, wherein the protocol is one of a plurality of protocolsutilizing the physical link.

In at least one example, the type comprises link layer packet data.

In at least one example, the data is to facilitate link statetransitions for the physical link.

In at least one example, the physical layer logic is further to decodethe stream signal to identify which of a plurality of differentprotocols applies to the data.

In at least one example, the physical layer logic is further to pass thedata to upper layer protocol logic corresponding to a particular one ofthe plurality of protocols identified in the stream signal.

In at least one example, the apparatus includes link layer logic andother upper layer logic of each of the plurality of protocols inaddition to the physical layer logic.

In at least one example, the plurality of protocols include at least twoof Peripheral Component Interconnect (PCI), PCI Express (PCIe), IntelIn-Die Interconnect (IDI), and Quick Path Interconnect (QPI).

In at least one example, the physical layer logic is further todetermine errors in each of the plurality of protocols

In at least one example, the physical layer logic is further todetermine errors in one or more of the valid signal and the streamsignal.

In at least one example, the physical layer logic is further to define adata window for data to be sent on the data lanes, and the data windowcorresponds to the valid signal.

In at least one example, the data window corresponds to a data symboland the valid signal is to be asserted in a window immediately precedingthe window in which the data is to be sent.

In at least one example, data is to be ignored on data lanes in a windowimmediately following a preceding window in which the valid signal isnot asserted.

In at least one example, the window corresponds to a byte time period.

In at least one example, each of the valid signal, data, and the streamsignal are aligned according to data windows defined for the physicallink.

In at least one example, the stream signal is to be sent during the samewindow as the data.

In at least one example, the physical link connects two devices in amulti-chip package.

In at least one example, the physical layer logic is further to recentersignals on the lanes of the physical link.

In at least one example, the lanes are to be recentered based on thevalid signal.

In at least one example, a stream signal is received on a dedicatedstream signal lane of the data link during a second window, the streamsignal is decoded, and a protocol associated with the data is determinedfrom the decoding of the stream signal.

In at least one example, the data link is adapted to transmit data of aplurality of different protocols.

In at least one example, data to be sent on the data link is identified,a valid signal is sent on an outgoing valid signal lane of the data linkduring a particular window corresponding to the data to be sent, and thedata is sent on dedicated outgoing data lanes during another windowimmediately subsequent to the particular window.

In at least one example, the plurality of data lanes further include adedicated link state machine sideband lane.

In at least one example, the first device comprises a first die in apackage and the second device comprises a second die in the package.

In at least one example, the first device comprises an on-package deviceand the second device comprises an off-package device.

One or more embodiments may provide an apparatus, a system, a machinereadable storage, a machine readable medium, hardware- and/orsoftware-based logic, and a method to identify data to be sent ondedicated data lanes of a data link, send a valid signal on a dedicatedvalid signal lane of the data link during a particular window thatcorresponds to data to be sent on the data link, send the data ondedicated data lanes of the data link during another window immediatelysubsequent to the particular window, and send a stream signal on astream signal link that is encoded to identify a type of the data.

In at least one example, the valid signal is to indicate that data onthe data lanes during the other window is valid data.

In at least one example, the stream signal link comprises a dedicatedstream signal link.

In at least one example, the stream signal is adapted to identifywhether a particular protocol is associated with the data.

In at least one example, the physical layer logic is included in acommon physical layer and a plurality of protocols utilize the commonphysical layer, and the particular protocol is included in the pluralityof protocols.

In at least one example, the plurality of protocols include two or moreof PCI, PCIe, IDI, and QPI.

In at least one example, the stream signal is further adapted toidentify whether the data comprises link layer packets.

In at least one example, the stream signal is further adapted toidentify whether the data sideband data.

In at least one example, the physical layer logic is further todetermine the type of the data and encode the stream signal to identifythe determined type.

In at least one example, the physical layer logic is further to sendlink state machine side band (LSM_SB) signals on a dedicated LSM_SB laneof the data link.

In at least one example, the physical layer logic is further to sendsideband signals on a sideband link separate from the data link.

In at least one example, the physical layer logic is further to sendlink layer data on the data lanes, wherein the link layer data is usedto transition the data link from a first link state to a second linkstate.

In at least one example, the first link state comprises an active linkstate and the second link state comprises a low power link state.

In at least one example, the physical layer logic is further to identifya first data window corresponding to the valid signal and send the dataon the data lanes within a second data window immediately subsequent tothe first data window.

In at least one example, not asserting the valid signal indicates thatdata on the data lanes in an immediately subsequent window is to beignored as invalid.

In at least one example, each of the first and second data windows isdefined to correspond to a byte time period.

In at least one example, each of the valid signal, data, and the streamsignal are aligned according to data windows defined for the physicallink.

In at least one example, the stream signal is to be sent during the samewindow as the data.

In at least one example, the physical layer logic is further to generateeach of the valid and the stream signal.

In at least one example, the data link connects two devices in amulti-chip package.

In at least one example, the data link is to support data speedsexceeding 8 Gb/s.

One or more embodiments may provide an apparatus, a system, a machinereadable storage, a machine readable medium, hardware- and/orsoftware-based logic, and a method to provide single-ended signaling ona data link including a plurality of lanes including a plurality of datalanes, one or more valid signal lanes, one or more stream lanes, anddistribute a clock signal for use by the plurality of lanes, wheresignals sent on each of the plurality of lanes are to be aligned withthe clock signal.

In at least one example, each of the data lanes is terminated mid-railto a regulated voltage.

In at least one example, the regulated voltage is provided for each ofthe plurality of data lanes by a single voltage regulator.

In at least one example, the regulated voltage is substantially equal toVcc/2, where Vcc comprises a supply voltage.

In at least one example, the physical layer logic is to attempt toprovide crosstalk cancellation between two or more of the plurality ofdata lanes.

In at least one example, crosstalk cancellation is provided by adding aweighted high-pass filtered aggressor signal on a first of the two ormore data lanes to the signal of a second of the two or more data lanes.

In at least one example, the physical layer logic is to generate theweighted high-pass filtered aggressor signal at least in part using aresistor-capacitor (RC) low pass filter.

In at least one example, the physical layer logic is to provide per bitduty cycle correction.

In at least one example, the physical layer logic is to detect skew onat least a particular one of the data lanes and deskew the particulardata lane.

In at least one example, the physical layer logic is further to apply ACdata bus inversion (DBI) to at least one of the data lanes.

In at least one example, the clock signal comprises a half rateforwarded clock signal.

In at least one example, the physical layer logic is further to provideelectrostatic discharge protection.

In at least one example, the physical layer logic is implemented atleast in part through hardware circuits.

In at least one example, valid signals are to be transmitted on thevalid signal lanes and each valid signal identifies that valid data isto follow assertion of the valid signal on the plurality of data lanes,and stream signals are to be transmitted on the stream signal lanes andeach stream signal identifies a type of the data on the one or more datalanes.

In at least one example, the data link is to support data speedsexceeding 8 Gb/s.

One or more embodiments may provide an apparatus, a system, a machinereadable storage, a machine readable medium, hardware- and/orsoftware-based logic, and a method to provide single-ended signaling ona data link including a plurality of lanes including a plurality of datalanes, one or more valid signal lanes, one or more stream lanes, and oneor more link state machine sideband lanes, distribute a clock signal foruse by the plurality of lanes, wherein signals sent on each of theplurality of lanes are to be aligned with the clock signal, providecrosstalk cancellation between two or more of the plurality of datalanes, and provide per bit duty cycle correction for the data link,where each of the data lanes is terminated mid-rail to a regulatedvoltage.

In at least one example, the physical layer logic is further to detectskew on at least a particular one of the data lanes and deskew theparticular data lane.

One or more embodiments may provide an apparatus, a system, a machinereadable storage, a machine readable medium, hardware- and/orsoftware-based logic, and a method to identify that respective upperlayers of each of a plurality of layered protocols request transition ofa data link from an active link state to a low power link state, whereineach of the plurality of layered protocols is to utilize the data linkas a physical layer, and transition the data link from the active linkstate to the low power link state based on an identification that theupper layers of each of the plurality of layered protocols requesttransition to the low power link state.

In at least one example, the physical layer logic is further toparticipate in a handshake with another device to cause the data link totransition to the low power link state.

In at least one example, the handshake comprises a link layer handshake.

In at least one example, the physical layer logic is to send link layerdata in the link layer handshake while the data link is the active linkstate.

In at least one example, the physical layer logic is to send a streamsignal substantially concurrent with the link layer data to identifythat data sent on data layers of the data link comprise link layerpackets.

In at least one example, the stream signal is sent on a dedicated streamsignal lane of the data link during a particular window, wherein thelink layer data is also sent during the particular window.

In at least one example, the physical layer logic is to send a validsignal on a dedicated valid signal lane of the data link, wherein thevalid signal is sent in another window immediately preceding theparticular window to indicate that data sent in the particular window isvalid.

In at least one example, the handshake comprises a handshakecommunication over a sideband link.

In at least one example, the handshake comprises a link layer handshakeand the handshake communication over the sideband link.

In at least one example, the handshake communication over the sidebandlink confirms the link layer handshake.

In at least one example, the physical layer logic is further to identifya request to transition the data link from the active link state to thelow power link state from an upper layer of a first one of the pluralityof layered protocols.

In at least one example, the physical layer logic is further to wait totransition the data link from the active link state to the low powerlink state until requests are received from each of other protocol inthe plurality of layered protocols.

In at least one example, the physical layer logic is to track, for eachof the plurality of layered protocols, whether the protocol hasrequested to transition the data link from the active link state to thelow power link state.

In at least one example, the physical layer logic is further to generatea response to the request confirming transition of the data link fromthe active link state to the low power link state prior to the actualtransition of the data link from the active link state to the low powerlink state.

In at least one example, the response is sent while approval of thetransition of the data link from the active link state to the low powerlink state is outstanding from one or more of the other protocols in theplurality of layered protocols.

In at least one example, the low power link state comprises an idle linkstate.

In at least one example, the plurality of layered protocols include oneor more of PCI, PCIe, IDI, and QPI.

A system can be provided to include a data link comprising a pluralityof lanes, first device, and a second device communicatively coupled tothe first device using the data link, the second device including upperlayer logic of a first protocol, upper layer logic of a second protocol,where each of the plurality of protocol stacks utilize a common physicallayer, and physical layer logic for the common physical layer, whereinthe physical layer logic is to determine that each of the protocols,including the first and second protocols, utilizing the data linkapproves transitioning the data link from an active link state to a lowpower link state prior to transitioning the data link to the low powerlink state.

In at least one example, the plurality of lanes include a plurality ofdata lanes, one or more valid signal lanes, one or more stream lanes.

In at least one example, valid signals are to be transmitted on thevalid signal lanes and each valid signal identifies that valid data isto follow assertion of the valid signal on the plurality of data lanes,and stream signals are to be transmitted on the stream signal lanes andeach stream signal identifies a type of the data on the one or more datalanes.

In at least one example, transitioning the data link to the low powerlink state comprises a handshake between the first and second devices.

In at least one example, the handshake comprises a link layer handshakeand sideband handshake.

In at least one example, the first device comprises a first die in apackage and the second device comprises a second die in the package.

In at least one example, the first device comprises an on-package deviceand the second device comprises an off-package device.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, theappearances of the phrases “in one embodiment” or “in an embodiment” invarious places throughout this specification are not necessarily allreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in any suitable manner inone or more embodiments.

In the foregoing specification, a detailed description has been givenwith reference to specific exemplary embodiments. It will, however, beevident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention asset forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense. Furthermore, the foregoing use of embodiment andother exemplarily language does not necessarily refer to the sameembodiment or the same example, but may refer to different and distinctembodiments, as well as potentially the same embodiment.

1-30. (canceled)
 31. An apparatus comprising: physical layer logic to:receive data on one or more data lanes of a physical link; receive avalid signal on another of the lanes of the physical link, wherein thevalid signal is to identify that valid data is to follow assertion ofthe valid signal on the one or more data lanes; and receive a streamsignal on another of the lanes of the physical link, wherein the streamsignal is to identify a type of the data on the one or more data lanes.32. The apparatus of claim 31, wherein the physical layer logic isfurther to send a link state machine management signal over another ofthe lanes of the physical link.
 33. The apparatus of claim 31, whereinthe physical layer logic is further to send a sideband signal over asideband link.
 34. The apparatus of claim 31, wherein the type comprisesa protocol associated with the data, wherein the protocol is one of aplurality of protocols utilizing the physical link.
 35. The apparatus ofclaim 31, wherein the type comprises link layer packet data.
 36. Theapparatus of claim 35, wherein the data is to facilitate link statetransitions for the physical link.
 37. The apparatus of claim 31,wherein the physical layer logic is further to decode the stream signalto identify which of a plurality of different protocols applies to thedata.
 38. The apparatus of claim 37, wherein the physical layer logic isfurther to pass the data to upper layer protocol logic corresponding toa particular one of the plurality of protocols identified in the streamsignal.
 39. The apparatus of claim 38, wherein the apparatus furthercomprises upper layer logic of each of the plurality of protocols. 40.The apparatus of claim 37, wherein the plurality of protocols include atleast two of Peripheral Component Interconnect (PCI), PCI Express(PCIe), Intel In-Die Interconnect (IDI), and Quick Path Interconnect(QPI).
 41. The apparatus of claim 37, wherein the physical layer logicis further to determine errors in each of the plurality of protocols 42.The apparatus of claim 41, wherein the physical layer logic is furtherto determine errors in one or more of the valid signal and the streamsignal.
 43. The apparatus of claim 31, wherein the physical layer logicis further to define a data window for data to be sent on the datalanes, and the data window corresponds to the valid signal.
 44. Theapparatus of claim 43, wherein the data window corresponds to a datasymbol and the valid signal is to be asserted in a window immediatelypreceding the window in which the data is to be sent.
 45. The apparatusof claim 44, wherein data is to be ignored on data lanes in a windowimmediately following a preceding window in which the valid signal isnot asserted.
 46. The apparatus of claim 43, wherein each of the validsignal, data, and the stream signal are aligned according to datawindows defined for the physical link and the stream signal is to besent during the same window as the data.
 47. The apparatus of claim 31,wherein the physical link connects two devices in a multi-chip package.48. The apparatus of claim 31, wherein the physical layer logic isfurther to recenter signals on the lanes of the physical link based onthe valid signal.
 49. A method comprising: receiving a valid signal on adedicated valid signal lane in a first window, wherein the valid signallane is one of a plurality of lanes in a data link; receiving data ondedicated data lanes in the data link during a subsequent second window;and determining that the data received during the subsequent secondwindow is valid based on the valid signal during the first window.
 50. Asystem comprising: an interconnect comprising a plurality of lanes,wherein the plurality of lanes include a plurality of dedicated datalanes, at least one dedicated valid signal lane, and at least one streamsignal lane; a first device; and a second device communicatively coupledto the first device using the interconnect, wherein the second devicecomprises logical physical layer logic to: receive data on the pluralityof data lanes; receive a valid signal on the valid signal lane, whereinthe valid signal identifies that valid data is to follow assertion ofthe valid signal on the plurality of data lanes; and receive a streamsignal on the stream signal lane, wherein the stream signal identifies atype of the data on the plurality of data lanes.